Parliament's watchdog on public account on Friday said it had instructed the Transnet board and management to curb graft at the state owned company.

"The Standing Committee on Public Accounts (Scopa) has told the Transnet Board and management to stop the looting because the business is able to sustain itself very well because it makes money due to it being a monopoly," Scopa said in a statement. 

"The alleged corruption and looting of resources is what is impacting negatively on Transnet."

The comments by Scopa came after its members of Parliament (MPs) conducted an oversight visit at Transnet's headquarters in Johannesburg, which coincided with the board  serving notices of suspension on chief executive Siyabonga Gama and two other top senior officials. 

Gama, chief procurement officer Thamsanqa Jiyana and supply chain manager Lindiwe Mdletshe have been given until Monday to give reasons why they should not be suspended.

The board moved against the three after reports from Werksmans Attorneys and forensic investigators revealed "various acts of possible misconduct against the three employees" and recommended further investigations be carried out to establish the extent of it, Transnet had said in a statement.

The state-owned transport and logistics company is at the centre of an investigation by authorities over possible fraud, corruption and money laundering regarding the procurement of locomotives. The "state-capture" is linked to the fugitive Gupta family and involves and amount of R38.6 billion.

Scopa said it noted the breakdown in internal controls after the entity received a qualified audit opinion for 2017/18.

"The committee has requested Transnet to give Scopa reports on internal audit reports that were changed or rejected by the previous internal audit committee. Scopa would like to check to see whether the members of that previous audit committee should not be blacklisted from holding non-executive positions in the public sector."

MPs also requested access to the Werksmans report and other forensic investigations report to monitor the implemention of recommendations in the documents.