NEW : One sailor remains hospitalized , the Navy says . NEW : Seven people have been treated and released . -- The U.S. Coast Guard is investigating a collision between two cargo ships in the Gulf of Mexico that left one person dead and three others missing off Louisiana. Damage is contained in boathouse area , the Navy says .
NEW : One sailor remains hospitalized , the Navy says . NEW : Seven people have been treated and released . A blast occurs as maintenance work is done on a vessel at a weapons station , the Navy says . Damage is contained in boathouse area , the Navy says .