White Mountains Insurance Group Ltd, the Bermudian-domiciled financial services holding company, has announced the preliminary results of its "modified Dutch auction" tender offer to purchase up to $500 million in value of its common shares.

The tender offer expired at midnight, New York City time, at the end of the day on Tuesday.

Based on a preliminary count by the depositary for the tender offer, 333,878 shares were properly tendered and not properly withdrawn at or below the purchase price of $1,400 per share, including 74,546 shares that were tendered by notice of guaranteed delivery.

The company said it expects to purchase all validly tendered shares for approximately $467.4 million.

The shares expected to be purchased in the tender offer represent approximately 11.5 per cent of White Mountains's shares outstanding as of August 19.

The number of shares expected to be purchased in the tender offer and the purchase price are preliminary and subject to change, the company said.

The preliminary information is subject to confirmation by the depositary and is based on the assumption that all shares tendered by notice of guaranteed delivery will be delivered within the two trading day settlement period.

The final number of shares to be purchased and the final purchase price will be announced promptly following the expiration of the guaranteed delivery period and completion by the depositary of the confirmation process.