NEW YORK—American International Group Inc. said Monday that it raised $452 million through the sale of its remaining ownership of reinsurer Transatlantic Holdings Inc.

The nearly 8.5 million shares of common stock were owned by AIG unit American Home Assurance Co.

AIG announced plans for a secondary public offering earlier this month. As previously announced, Transatlantic Holdings bought 2 million of the shares owned by American Home Assurance in the offering, AIG said.

The deal closes out AIG’s ownership of Transatlantic, which AIG in June 2009 reduced to approximately 13% from a majority stake of roughly 59%.