Cypress Group has sold its investment in Montpelier Re Holdings Ltd. which it helped form after September 11 terrorist attacks, more than doubling its money in three years.

On Tuesday, Montpelier said founding shareholders including Cypress and a DLJ Merchant Banking fund had sold 3.7 million shares at $41.80. Goldman, Sachs & Co. acted as sole manager on the sale. DLJ still retains a 2.2 percent stake.

Cypress had sold down its Montpelier stake over time in three earlier sales. Cypress? internal rate of return on the investment was nearly 37 percent, a source told www.thedeal.com, and it made about 2.2 times its investment.

Before the latest sale, Cypress held 3.8 percent and DLJ 4.4 percent, according to securities filings.

In December 2001, White Mountains Insurance Group Ltd. and Benfield Group Plc founded Montpelier, with about $1 billion in capital, including $150 million of equity from Cypress. It went public in October, 2002.

Montpelier did not sell any stock in the offering this week, according to a statement. Spokesmen at Credit Suisse First Boston, DLJ Merchant Banking?s parent, and at Goldman declined comment on Tuesday. Calls to Montpelier were not returned.

?We are pleased to have been involved in the founding and building of Montpelier,? Cypress president William Spiegel said. ?Over the last three years, Tony Taylor and his team have built Montpelier into one of world?s leading property reinsurance companies. We believe the company has a very bright future.?

Last month Blackstone, which invested $200 million in , sold its remaining shares.