Details are emerging of the shadowy life of former South African Defence Force major-general Tai Minnaar, who died in suspicious circumstances last September.

Minnaar was named this week as part of a team that claims to have documentary evidence showing that South African security forces carried out the 1986 murder of the Swedish Prime Minister Olof Palme.

But it was Minnaar's involvement last year in an extraordinary series of deals to try to sell South African biological warfare expertise that probably cost him his life.

On the night of September 9 Minnaar (62) died in the arms of his fiancée, Romay Harding, at his home in Pretoria. Harding is understood to be in hiding somewhere in the Cape.

Though the official cause of death was noted as a heart attack, Harding told investigators that Minnaar had been vomiting before his death and that his corpse had swollen rapidly to more than double its normal size. She however declined to make a formal statement.

The cremation of Minnaar's body seems to have put paid to further investigation, but such swelling is characteristic of some of the exotic poisons Minnaar was alleged to be peddling in the months before his death.

Early last year Minnaar had become involved in increasingly desperate attempts to do a deal involving substances and technology developed under South Africa's once-secret and now notorious chemical and biological weapons programme, dubbed Project Coast, led by Wouter Basson.

Project Coast was officially closed down in 1994 and its chemical and biological warfare products were supposedly destroyed to comply with international anti-proliferation treaties. Any access Minnaar had to anthrax spores could throw doubt on South Africa's non-proliferation credentials.

But back to the story: From November 2001, Minnaar, acting as a go-between for a group of former Project Coast scientists, tried to set up a series of commercial deals, beginning with two shady American agents allegedly claiming to represent the United States government.

When that fell through it appears that Minnaar and some of his associates tried to hijack the process from the scientists, procuring first a German Nazi treasure hunter as a possible buyer and then, finally, someone Minnaar apparently believed to be an Arab sheikh. The "sheikh" turned out to be part of a police sting operation aimed at uncovering Minnaar's activities.

The case was closed when Minnaar died, though a kilogram of potassium cyanide - enough to poison a city - was found among other chemicals at his home, according to sources close to the police investigation.

Daan Goosen, a former member of the Project Coast team involved in the saga, told the Mail and Guardian it all began legitimately enough with a trip early last year to the US research company Bioport, a privatised facility that has the exclusive contract to manufacture anthrax vaccine for the US government.

Goosen, who made a detailed disclosure of his activities to the Truth and Reconciliation Commission and was a state witness in the prosecution of Wouter Basson, has for some time been seeking legitimate avenues for some of his colleagues to use their skills for peaceful purposes.

Anti-proliferation experts have long noted the dangers of leaving scientists with bio-war knowhow to fend for themselves after state programmes are ended - and Goosen admits that some of his former colleagues have fallen on difficult times.

In the wake of the post-September 11 anthrax attacks in the US, therefore, Goosen says he made contact with the Pentagon to enquire about offering the services of former Project Coast scientists. He says he was referred to Bioport and undertook a trip there at the beginning of last year.

The US company brushed off his offer of open co-operation, a response he found puzzling. "We looked at their problems. They were in a shambles in respect of anthrax. We thought we could assist them with antidotes, antiserums and a vaccine for anthrax."

On his return an acquaintance put him in touch with Minnaar, who was introduced as a man who had worked with the Central Intelligence Agency and who could provide access to the right people. Minnaar's links with the CIA were well known in the intelligence community.

During the Eighties he worked under cover in Cuba in what appears to have been a joint operation between the CIA and South African military intelligence. He showed Goosen an award he said he had received from the CIA for his services.

Minnaar got in touch with two Americans, Don Mayes and Bob Zlockie, in March last year. Though Goosen met only Zlockie, both had the necessary pedigree for Goosen to believe they were acting as official US representatives.

Intelligence contacts told Goosen that Mayes was a former CIA agent and that Zlockie was still with the organisation.

The picture that has since emerged points to the possibility of something more sinister.

The M&G has established that Mayes gained notoriety in the 1990s when he ran a company called Vector Microwave Research.

In a 1998 article, The Washington Post stated: "For years, Vector had performed secret tasks for the CIA and the US military, using guile, experience and connections, including those of its president, retired Lieutenant-General Leonard Perroots, a former director of the US Defence Intelligence Agency."

The newspaper said Vector specialised in covertly acquiring foreign missiles, radar, artillery and other weapons for US intelligence agencies.

At the time of the Post article, Mayes was suspected of conducting "unauthorised" side deals - a charge he successfully parried - raising the spectre that he could have been dealing with Goosen and Minnaar as a free agent.

It is also understood that Mayes and Zlockie were both friends of Minnaar, having worked with him in South America in the 1980s.

Questions to the CIA about Mayes, Zlockie and their activities in South Africa were unanswered at the time of going to press.

Mayes could not be reached at his home in Florida. Zlockie told the M&G: "I have no interest in talking to you at all," before putting down the phone.

Goosen says he proposed that the Americans fund South African research to be conducted under the control of the civilian Centre for Disease Control in Atlanta. He claims that Zlockie insisted the work would have to be done in the US and would have to be covertly funded. He insisted the US government would not openly work with the South African scientists.

Goosen says he baulked at this, but in the meantime he had handed two samples to Zlockie - an antitoxin (like a serum) and a genetically modified organism used to produce a vaccine. Goosen insists that the material did not represent a proliferation threat.

From then the picture of what happened gets murky. Goosen says he travelled to China to help that country with an animal vaccine programme in April and May. When he came back, he found the deal with the Americans was off.

Minnaar, moreover, had in the meantime fallen in with Arnold van Eck, a former National Intelligence Agent who had left that organisation under a cloud.

According to a statement later prepared by Van Eck, Minnaar asked him to find another buyer for anthrax serum. Van Eck claims he came up with someone he had met in Czechoslovakia, Helmut Gaensel.

German-born Gaensel is a colourful character. A former Czech intelligence agent, he was employed to hunt for hidden Nazi treasure, until his defection to the West in the 1960s. In the early 1990s he made a living persuading investors to back his excavations of abandoned mines on the Czech border, still in pursuit of Nazi riches.

Like Mayes and Zlockie, Gaensel also moved to Florida, but could not be contacted.

According to Van Eck, Minnaar discussed selling not only serum to Gaensel but anthrax itself.

Goosen confirms he was asked to supply anthrax "for testing the serum" but says he refused. According to Van Eck's affidavit, he went to the police when talk of selling anthrax at the beginning of July last year emerged.

Police spokesperson Sally de Beer declined to comment on issues involving Minnaar, but police and intelligence sources have confirmed that a sting operation was launched, complete with a fake sheikh installed at a posh Johannesburg hotel.

This time Van Eck acted as the go-between for Minnaar, who, from transcripts of Minnaar's SMS messages seen by the M&G, seemed to have no idea he was being set up.

But Goosen again refused to supply anthrax and the sting collapsed.

Minnaar died, leaving a string of unanswered questions, including whether he met police National

Commissioner Jackie Selebi shortly before his death, as has been claimed in a news report last year on Minnaar's death. The transcripts of Minnaar's SMS messages indicate he intended to meet Selebi.

De Beer this week said that Selebi's position has been not to comment on the matter.

With acknowledgements to Sam Sole and the Mail and Guardian.