TOKYO, Nov 5 (Reuters) - Japanese buyout firm Unison Capital said on Thursday that government authorities have been investigating a possible case of insider trading involving a now-deceased former partner at the company.

Unison is one of Japan's largest and well-known private equity funds with investments of about 700 billion yen ($7.7 billion). It was founded by former Goldman Sachs Group Inc (GS.N: Quote, Profile, Research) bankers John Ehara and Tatsuya Hayashi.

The Securities and Exchange Surveillance Commission searched Unison's office in relation to the matter on Oct. 27, a spokeswoman for Unison said without elaborating.

The partner was fired that day and died on Oct. 28, she said, without revealing the partner's name or the cause of death.

The spokeswoman, who declined to be named because of the firm's policy on being quoted by media, said the company could not confirm whether the investigation had ended or was continuing.

Unison has set up a committee of three lawyers to investigate the incident and also examine the firm's standards of governance.

No one at the SESC was immediately available for comment.

Unison in August obtained commitments from investors of 140 billion yen for its third investment fund.

Earlier this year, it tried but failed to buy a 35 percent stake in a Japanese wig maker Aderans Holdings (8170.T: Quote, Profile, Research), being defeated in a battle with U.S. hedge fund Steel Partners. [ID:nT339345] ($1=90.60 Yen) (Reporting by Junko Fujita; Editing by Lincoln Feast)