May 15 (Reuters) - Warren Buffett's Berkshire Hathaway on Wednesday revealed a new, $6.72 billion stake in the insurer Chubb, ending months of speculation that it had made a big new investment.

In a regulatory filing describing its U.S.-listed stock holdings as of March 31, Berkshire said it owned 25.92 million shares of Chubb.

Berkshire had previously obtained permission from the U.S. Securities and Exchange Commission to temporarily keep the investment confidential.

It occasionally requests such treatment when it makes big investments, because investors often try to piggyback on Berkshire before it's done buying. (Reporting by Jonathan Stempel in New York; editing by Jonathan Oatis)