Navy assault ship, tanker collide; no injuries Updated 5:45 p.m. (AP) SAN DIEGO - A U.S. Navy amphibious assault ship and a refueling tanker collided in the Pacific Ocean on Wednesday but there were no injuries and no fuel spills, the Third Fleet said. The collision between the assault ship USS Essex and the oiler USNS Yukon occurred at midmorning about 120 miles off Southern California, according to a statement. The Navy said an apparent steering malfunction occurred as Essex approached the Yukon. Neither ship's fuel tanks or systems were compromised, but the Navy said a full assessment of any damage is continuing. The Essex is due to return to San Diego on Thursday after 12 years based in Sasebo, Japan. The Yukon is a 677-foot tanker that replenishes oil for other Navy ships in the Pacific fleet. It was launched in 1993, and all but three of its 92 crew members are civilians, according to the Navy's website.