White Mountains Re, a unit of Bermuda-based White Mountains Group, said it was selling subsidiary Sirius America Insurance Co. to an investor group for some $139 million.

White Mountains, under the terms of the sale, will acquire an 18 percent stake in the investment group. Other members include Lightyear Capital Llc, a private equity firm, a unit of Lehman Brothers Holdings Inc., and AlpInvest Partners.

The Sirius America sale didn't appear to include Sirius International, another unit that was banned from selling policies in Florida after breaking licensing laws in that state.

White Mountains acquired Sirius America two years ago as part of its acquisition of the Sirius Group. The sale is expected to close in the second quarter of this year.

White Mountains' shares fell $6.20, in composite trading yesterday on the New York Stock Exchange, to close down 1.12 percent at $547.