Japanese investigators on Wednesday seized a lot of confidential documents during a raid at the headquarters of disgraced camera-maker Olympus Corp.

Dozens of dark-suited investigators poured into the headquarters and came out many hours later with boxes full of documents. The raid was a part of an ongoing investigation into the camera & medical equipment maker's $1.5-billion accounting scandal.

The home of Olympus Corp.'s former president Tsuyoshi Kikukawa, who is suspected of helping the accounting scandal, was also raided.

The accounting scandal came to light in October when Olympus' former chief executive Michael Woodford blew the whistle over outlandish accounting practices that were used to hide losses of around $1.5 billion over the past two decades.

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

The company also assured that it would provide full cooperation to the investigators.Olympus Corp. could be delisted from the Tokyo Stock Exchange if the criminal investigation discovers serious offences.