"We did have a report of an oil sheen which might be consistent with fuel from the fighter jet itself and we have also had a report of a small amount of debris," said Capt. Michael McAllister, commander of Coast Guard Sector Charleston.
The search was expanded from 750 to 1,300 square miles as Coast Guard and Air Force aircraft joined vessels from the Coast Guard, Navy, law enforcement and commercial shippers searching for Capt. Nicholas Giglio. He is based at Shaw Air Force Base in Sumter.
McAllister, who said he did not know exactly what the debris was, said there would have been a tracking beacon both on the pilot and his ejection seat, but no signal has been picked up.
"We presume there is a pilot who is in the water and needs to be rescued," he said. "The lack of a beacon might indicate that the pilot didn't safety eject or that there was an equipment malfunction. It makes it more difficult for us since we don't have the beacon to hone in on."
The planes collided Thursday around 8:30 p.m. about 40 miles off the South Carolina coast, said Senior Master Sgt. Brad Fallin at Shaw Air Force Base. Both jets, based at Shaw, are single-seat aircraft.
The jet piloted by Capt. Lee Bryant landed safely at Charleston Air Force Base, Fallin said. Bryant was examined at the base but suffered no injuries and was released.
McAllister said visibility was good and winds were about 25 mph at the time of the collision. He said he did not think it was raining at the time.
The water temperatures in the crash area were about 75 degrees and most people could survive 24 hours, he said.
"Given that this was a military member they would probably be in good shape and have a will to live. We would expect it would be quite a bit more than the 24 hours," McAllister said.
The pilots' hometowns and ages were not immediately available.
Fallin said he didn't know how much damage Bryant's plane sustained and that it was being examined as part of the investigation.
Earlier this week, Shaw Air Force Base announced that pilots would be conducting nighttime exercises to allow pilots to fly with night vision equipment and practice tactics critical to surviving in combat.