The latest investigation ordered into shredded parliamentary documents, which it was hoped would shed light on payments by controversial Durban businessman Schabir Shaik to former transport minister Mac Maharaj's wife, Zarina, looks instead to be deepening the mystery.

National assembly speaker Frene Ginwala said this week she had ordered a probe into the shredding, but several sources have told Independent Newspapers that parliament had already investigated the matter earlier this year and a report had been handed to Ginwala.

"There was an earlier investigation into the shredding, and Madame Speaker knew about it," said one of the sources.

However, Ginwala denied any knowledge of it while parliament's top official, Sindiso Mfenyana, offered an abrupt "no comment" as a response to questions about the earlier probe.

"I know nothing about it," Ginwala said late on Friday, adding that her investigation was continuing.

Professor Kader Asmal, who chaired the committee on members' interests when it discussed, during 1996/97, the shredding of the documents, has also refused to comment.

Despite numerous requests to his office throughout the week, Asmal has not come forward to explain his side of the story.

According to an investigation by FirstRand, the bank from which Maharaj resigned last week, payments totalling R328 989 were made "for consultancy work" to his wife, through her company Flisan Consulting, by Shaik and his Nkobi Holdings group of companies.

Maharaj was obliged to declare the payments to his wife in the confidential section of the register of member's interests, but it came to light this week that parts of the register had been destroyed.

The elite Scorpions unit is investigating charges against Maharaj for the payments received from Shaik between 1996 and 2000 - Maharaj was transport minister from 1994 to 1999.

Shaik's companies benefited from multibillion-rand government contracts for the N3 toll-road concession and the credit card licence system.

Maharaj has insisted that he was "not involved in any bribery and corruption".

The South African Revenue Service (SARS) should also be able to shed new light on the reasons for the payments as an investigation into the tax affairs of Maharaj, his wife and Shaik will be able to give details of the deposits.

However, SARS would not comment on whether it had indeed launched an investigation, saying the affairs of taxpayers were confidential unless they became part of court proceedings.

Asked whether SARS was not obliged to investigate, given the allegations of corruption, spokesperson Sechaba ka Nkosi said SARS was able to undertake "investigations of tax compliance or non-compliance with the tax laws" and would co-operate with other state agencies such as the Scorpions.

With acknowledgements to Jeremy Michaels and the Weekend Argus.