South Korean police on Thursday raided the main office of BMW Korea, the local unit of German carmaker BMW, on probe into whether it hid vehicle defects causing engine fires.

About 30 investigators stormed the BMW Korea office earlier in the day, according to local media reports.

It came three weeks after tens of BMW vehicle owners filed the case with the Seoul police, claiming the automaker may have concealed documents relevant to the engine fires.

About 40 BMW vehicles have caught fire this year though no injury nor fatality was reported.

The German carmaker blamed the exhaust gas recirculation (EGR), a component to reduce nitrogen oxide emissions, for the recent engine fires, but some of vehicle owners suspected BMW may have hidden the real cause of the fires.

BMW Korea began a voluntary recall of more than 106,000 vehicles last week, but fire accident was reported from BMW vehicles not subject to the recall.

A total of 1,226 BMW vehicle owners reportedly planned to file a damages suit with the Seoul Central District Court Friday against the German automaker, seeking 15 million won (13,500 U.S. dollars) in compensation each.