The U.S. military is continuing its search for the pilot of a U.S. Navy F/A-18C Hornet fighter jet that went down in southern Iraq on Wednesday.

The F/A-18C went down near Karbala, a city about 80 kilometers south of Baghdad where fighting continued between U.S. Army forces and the Iraqi Republican Guard. The single-seat jet, flying from the aircraft carrier USS Kitty Hawk, went down at about 3:45 p.m. E.S.T., officials said.

While the cause of the crash is under investigation, initial reports say the jet was shot down by an Iraqi surface-to-air missile. If early reports are correct, the incident would mark the first downing of a coalition fixed-wing plane due to enemy fire during the two-week old air campaign.

Meanwhile, Brig. Gen. Vincent Brooks this morning was asked at U.S. Central Command briefing in Qatar if a Patriot missile may have downed the plane. Brooks would not confirm. He said: "It's too early for me to be able to determine what the cause was."

A British Tornado jet was shot down last week by a Patriot, killing both crewmen aboard.