WATCH LIVE | Former Transnet employee Gerhard van der Westhuizen next in the State Capture hot seat

Up next in the Zondo commission hot seat is former Transnet employee Gerhard van der Westhuizen.

Last week former Transnet electrical engineer Francis Callard admitted to the Zondo commission that an increase of about R1bn in the cost of 100 locomotives from China South Rail (CSR) was "excessive and difficult to justify".

Callard revealed that he was instructed in April 2014 by Transnet's then executive finance manager Yousuf Laher to draft a memorandum for the increase in the estimated total costs payable to the Chinese consortium from R3.8bn to R4.8bn.

This was for the controversial purchase of 100 electric locomotives.

Deputy chief justice Raymond Zondo instructed the commission's legal team on Friday to contact the Hawks over damning testimony related to the tainted Transnet deal for locomotives. 

Roberto Gonsalves, whose company was part of the CNR Consortium that entered into an agreement with Transnet on March 17 for the supply of 232 of the 465 diesel locomotives at a contract price of R42m per locomotive, also testified before the inquiry. The total cost was R9.7bn.

Gonsalves told the commission how, about 10 days before the consortium submitted its final tender documents, a request came through from Transnet for the project to be moved from Pretoria to Durban.

"We changed our prices accordingly, which added up to R9.7bn in our final documents," he said.