OneBeacon Insurance Group Ltd., a specialty insurer controlled by White Mountains Insurance Group Ltd., is exploring a sale, according to people with knowledge of the matter.

OneBeacon has drawn interest from companies including China’s Fosun International Ltd., said the people, who asked not to be identified because the matter is not public. White Mountains, which owns about 75 percent of OneBeacon, is informally approaching the bidders and won’t sell the business if it can’t fetch a high enough price, the sources said.

OneBeacon rose 11.3 percent to $16.69 as of 10:04 a.m in New York trading Wednesday, giving the Bermuda-based company a market value of $1.6 billion. The insurer’s offerings range from coverage against shipping losses to policies that repay funds spent on college tuition if students don’t finish school.

White Mountains is testing the market for OneBeacon as insurance companies bulk up in the face of new competition from hedge funds. Earlier this year PartnerRe Ltd. and AXIS Capital Holdings Ltd. agreed to merge, and XL Group Plc said it would buy Catlin Group Ltd. for about $4 billion.

Fosun is an investment company with holdings in a variety of industries including insurance and real estate. China’s insurers, including Fosun and Anbang Insurance Group Co., have been on a global buying spree, acquiring rivals in Europe and property in the U.S.

Representatives for White Mountains and Fosun declined to comment.