SAfrica antitrust watchdog raids cement makers

* Raids PPC, Lafarge, Afrisam, Natal Portland Cement

* Probe started 2 years ago, will prosecute guilty producers

* PPC says co-operating with commission

JOHANNESBURG, June 25 (Reuters) - South Africa's Competition Commission said on Thursday it had raided the offices of cement makers as part of its investigation into price fixing and market allocation in the industry.

The commission searched the offices of Pretoria Portland Cement (PPCJ.J), Lafarge Industries South Africa (a unit of French cement company Lafarge (LAFP.PA)), Afrisam and Natal Portland Cement Cimpor.

"During the search we seized documentation and electronic data, which we will now evaluate as part of our investigation. Should we find that the firms have engaged in anti-competitive conduct, we will prosecute them for breaking the law," said commissioner Shan Ramburuth.

The commission said the probe, which has been going on for two years, found cement producers had been increasing prices in tandem every six months at levels higher than producer price inflation.

PPC, Africa's biggest cement maker, said it had always been vigilant in ensuring compliance with competition laws and was co-operating with the commission.

"Whilst reserving its rights, PPC is co-operating with the Commission," the company said in a brief statement. (Reporting by Tiisetso Motsoeneng; Editing by David Holmes)