Former Transnet electrical engineer Francis Callard resumed his testimony at the commission of inquiry into allegations of state capture on Monday.
On Friday he told the commission it was "unusual" for China South Rail (CSR) to receive a 60% upfront payment for a locomotive contract with Transnet.
Callard provided evidence on a contract awarded to CSR awarded in 2014 to provide Transnet with 100 locomotives.
He also told the commission, chaired by Deputy Chief Justice Raymond Zondo, that the procurement process was rigged for CSR to get the contract.
Last week commission chairperson, Deputy Chief Justice Raymond Zondo, said there appeared to have been a "blatant" disregard for processes put in place to protect Transnet against abuse, corruption and to minimise its losses.