Japanese prosecutors raided Olympus Corp units on Wednesday in connection with a huge accounting scandal that has threatened the existence of the 92-year-old maker of cameras and medical equipment, Japanese media reported.

A spokeswoman for the Tokyo district prosecutors office could not confirm the reports.

Tokyo prosecutors, police and the Securities and Exchange Surveillance Commission have joined in a rare joint probe of Olympus' 13-year, $1.7 billion scheme to hide investment losses stretching back two decades.

Prosecutors began raiding three units acquired by Olympus as part of the loss-making scheme, public broadcaster NHK said. Raids are expected later in the day at Olympus headquarters, it added.

A panel of experts appointed by Olympus to probe the scandal reported earlier this month that former Executive Vice President Hisashi Mori and ex-internal auditor Hideo Yamada masterminded the scheme with the help of investment bankers, and that three ex-presidents including Tsuyoshi Kikukawa had known about the cover-up.

Olympus last week filed five years' worth of corrected statements, plus overdue first-half results, meeting a Tokyo Stock Exchange deadline to avoid a humiliating delisting, at least for now.

Former Olympus CEO Michael Woodford, who blew the whistle on the scandal after being axed in October, is campaigning to get his job back but faces a potential proxy fight with management, who want to pick their own successors.

(Reporting by Nobuhiro Kubo; Writing by Linda Sieg and Edmund Klamann; Editing by Chris Gallagher)