JAPANESE prosecutors raided the headquarters of Olympus Corp and the home of its former president yesterday as part of an investigation into the cover-up of massive losses at the camera and medical equipment maker.

A trail of dark-suited officials was shown on national television marching solemnly into the company's Tokyo office building.

Olympus said it would fully cooperate with the investigation. "We apologize deeply again for the great troubles and worries we have caused our shareholders, investors, customers and others," it said in a statement.

Tokyo prosecutors said the home of former president Tsuyoshi Kikukawa, who is suspected of helping to orchestrate the cover-up, was also raided, as were the offices of three companies used in the scheme.

The deception at Olympus dates back to the 1990s and involved an elaborate scheme to hide 117.7 billion yen (US$1.5 billion) in investment losses. It only came to light in October when then president Michael Woodford blew the whistle on what he thought was strange and excessive spending.

Woodford, a Briton, had been a rare foreigner to head a major Japanese company.Woodford was fired after he confronted the company's board of directors with his doubts. In recent weeks, he has been trying to stage a comeback to the top, by appealing to shareholders, employees and others that his return will work to clean up Olympus.

Olympus stock plunged amid the scandal but has recouped some of those losses recently. Yesterday it slipped 1.4 percent to 1,050 yen.