ADEN, Yemen (CNN) -- At least four Americans were killed, and dozens more were injured or missing Thursday after a possible terrorist attack on the Navy destroyer USS Cole in the Yemeni port of Aden.

The Pentagon said the Cole was hit from the rear by a small boat packed with explosives at about 12:15 p.m. (5:15 a.m. EDT/9:15 GMT). The resulting blast tore a large hole in the ship's hull and left the 505-foot-long Cole listing four degrees to its port side.