Shares in Japanese electronics giant Sanyo have sunk 21% on news that watchdogs are probing its accounts.
Sanyo is currently trying to turn around its business
The Securities and Exchange Surveillance Commission is investigating claims of financial window-dressing at the group.
According to reports, Sanyo is said to have falsified its 2003 report to post a small profit rather than a loss.
Sanyo confirmed an investigation was underway and said it was co-operating fully with the authorities
The company is the latest to be targeted by Japanese officials for alleged dubious accounting.
Major machinery maker Komatsu has also confirmed it is being investigated over allegations of insider trading over a 2005 share buyback, while former executives at internet services group Livedoor are on trial on charges of falsifying accounts.
News of the probe led to Sanyo shares sliding by as much as 29% on the Tokyo market. The shares eventually closed down 21% at 181 yen.
Sanyo refused to confirm a report in the Asahi Shimbun newspaper that it had considered writing off losses of 190bn yen ($1.6bn; £817m) in 2003, but had instead written off only 50bn yen.
The investigation comes as Sanyo is attempting to turn around its business.
In 2005, the group embarked on a three-year restructuring drive in an effort to reduce its losses and refocus its operations.
The shake-up has resulted in a management overhaul and 14,000 job cuts.