The Competition Commission's investigation into alleged construction tender bid rigging is still underway, it said on Friday.

The commission confirmed it had started the "Construction Fast Track Settlement Project (CSP)" on February 1, 2011.

At the time, it invited firms in the construction industry to disclose projects and tenders affected by bid-rigging conduct, in return for lower penalties.

It received applications from 21 firms in the construction industry. After the first phase assessment of all the applications, the commission identified 301 different projects and tenders that were subject to bid-rigging.

"These projects and tenders included some of the major infrastructure developments in South Africa, including some of the Soccer World Cup stadiums," commission spokeswoman Trudi Makhaya said.

"During the evaluation process, 24 firms that did not apply for settlement were also implicated in bid-rigging conduct. This conduct is currently being investigated."

The commission evaluated conditional leniency for the firms that had applied for settlement.

This evaluation process enabled the commission to determine the respective projects and tenders that the firms were liable to settle.

"The commission is expected to commence with the settlement negotiations with the respective firms in the near future," Makhaya said in response to questions.

A criminal investigation was separate from this, the commission said.

The Mail & Guardian reported that the commission, the Hawks and the National Prosecuting Authority (NPA) were investigating the matter, and named some of the country's biggest construction companies.

It reported that senior managers and executives could face jail time for activities that could be defined as fraud, corruption, or racketeering.

It reported that only one executive had been granted immunity by the NPA.

There was also concern about the effect the investigation would have on the industry, which was involved in one of the country's biggest ever construction roll-outs.

It quoted Hawks spokesman Paul Ramaloko as confirming the investigation, but saying he could not discuss the case.

"We are going to take our time and do a thorough investigation," the publication quoted him as saying.

Previously the commission had imposed massive fines on companies found to have participated in anti-competitive behaviour.