The U.S. Securities and Exchange Commission (SEC) has asked rating agency Standard & Poor's (S&P) to disclose which employees knew of its decision to downgrade U.S. debt before it was announced last week, the Financial Times said, citing people familiar with the matter.

SEC's move is part of a preliminary examination into potential insider trading, the FT said.

The inquiry was made by the SEC's examination staff, which has oversight of credit rating firms, one person familiar with the matter told the newspaper.

However, the securities regulator is not aware of a leak from an S&P insider, nor was it aware of an aberrational trade, the paper said.

S&P and SEC could not immediately be reached for comment by Reuters.

The U.S. Senate Banking committee has begun looking into last week's decision by S&P's to downgrade the U.S. credit rating, a committee aide told Reuters on Monday.

(Reuters)