Mr Greenberg has been at AIG since 1960 and led it since 1967

The chairman of the world's biggest insurance firm is to step down, weeks after giving up its day-to-day running.

In a letter from his lawyer, Maurice "Hank" Greenberg said he would end his four decades at the top of American International Group (AIG) within days.

AIG is one of several insurers being probed for suspicious transactions.

Mr Greenberg is one of 12 AIG directors who received subpoenas on Monday from the Securities and Exchange Commission, the US financial watchdog.

Mr Greenberg, who is 79, had been at the helm since 1967, turning AIG into a global operation with 50 million customers in 130 countries and a market value of $168.5bn.

He agreed to step down as chief executive on 15 March, although he stayed on as non-executive chairman.

That role, though, will now be filled by senior director Frank Zarb until a new chairman can be elected.

The SEC's is only the latest investigation into the US insurance industry.

The first was started by New York Attorney General Eliot Spitzer, into allegations that insurance companies bolstered their bottom line with reinsurance deals to shift risk off their balance sheets.

The initial interest in AIG was sparked by a 2000 transaction with General Re which could have boosted AIG's reserves.

But both Reuters and AP report that 10 other transactions have now come under the microscope.

Mr Spitzer praised AIG's recent actions in the wake of the probes and Mr Greenberg's agreement to leave the company.

"While there is a long way to go before this investigation is complete, the wise actions of the AIG board will help set this investigation on a path toward resolution," he said in an e-mailed statement.

"I commend the AIG board for acting in a way that sets it apart from other boards that have faced similar problems in recent years."

(BBC)

subpoena: a writ issued by court authority to compel the attendance of a witness at a judicial proceeding（传票）

bottom line :（账本底线）