Japan's main securities watchdog is looking into past Olympus M&A deals, focusing on whether the company made appropriate financial disclosures about them, two sources familiar with the matter said.

The endoscope and camera maker is mired in an escalating corporate governance scandal, with its former British CEO saying he was fired for questioning a $687 million payment to advisers in the $2.2 billion takeover of medical equipment maker Gyrus in 2008.

The monthly magazine Facta first raised red flags about Olympus M&A deals in its August edition, and the Securities and Exchange Surveillance Commission started paying particular attention to the company around that time, said the sources, who were not authorized to discuss the matter publicly. SESC officials declined to comment.

A senior Japanese lawmaker has called for probes by financial and securities watchdogs and urged Olympus to explain fees that could risk shareholders losing confidence in Japan.

(Reporting by Noriyuki Hirata; Writing by Taiga Uranaka; Editing by Joseph Radford)