NEW YORK (Bloomberg) — Marsh & McLennan Cos., the world's second-biggest insurance broker, received an offer for its Kroll security unit that values the subsidiary at $1.2 billion to $1.5 billion, said a person familiar with the matter.

The bid came from a private-equity firm, said the person, who declined to be identified because the matter is private. Buyout firms Carlyle Group, Apax Partners and General Atlantic LLC made bids that may result in a $1.3 billion sale, the Financial Times reported earlier.

Chief executive officer Brian Duperreault has been selling parts of Kroll, the least profitable of the company's divisions, and has written down the unit's value. A full sale would allow Marsh & McLennan, also known as MMC for its ticker at the New York Stock Exchange, to exit a peripheral business and focus on its insurance brokerage, said Meyer Shields, an analyst at Stifel Nicolaus & Co.

"I have yet to talk to the person who really likes MMC because of Kroll," Shields said yesterday in a telephone interview. "It's never fit in really, really well."

Kroll, purchased by Marsh & McLennan in 2004 for about $1.93 billion, conducts investigations to uncover fraud and locates misappropriated assets. The unit was hired by Kuwait in the 1990's to investigate Iraqi dictator Saddam Hussein's financial network used to hide funds.

Marsh & McLennan spokeswoman Christine Walton declined to comment to Bloomberg News. Carlyle spokesman Christopher Ullman also declined to comment, as did Ben Harding of Apax and Pat Hedley of General Atlantic.