"We're sensitive to the marketplace and the noise we're hearing in the marketplace," Mr. Cherkasky said in explaining why he was tightening control at Marsh's reinsurance unit.

Chief among those transactions, and one that has been a focus of the investigations, is a 2000 deal between A.I.G. and General Re, a reinsurance unit of Berkshire Hathaway.

Worries about losses at the reinsurance unit because of asbestos claims and those related to the terrorist attacks had been depressing G.E.'s stock.

Executives said the company remained disappointed in the lagging performance of the reinsurance unit, which provides protection for other insurance companies against catastrophic losses like weather disasters or large jury verdicts.

Building up A.I.G.'s reserves was the motivation behind a dubious transaction struck by the company in 2000 with General Re, a reinsurance unit of Berkshire Hathaway.

Her father is the president of Guy Carpenter, a reinsurance unit of the Marsh & McLennan Companies in New York.

Zurich Financial Services began trading its reinsurance unit, Converium Holding, in a $1.7 billion public offering, the biggest in Switzerland in several years.

The company also sold its reinsurance unit, renamed Converium Holding, raising some $2 billion.

The reinsurance units of Berkshire Hathaway, including General Re, reported sales of $10.6 billion followed by Hannover Re at $10.1 billion.

Mr. Dowling, 35, is an underwriter in Bernardsville, N.J., with the reinsurance unit of the Chubb Group of Insurance Companies.