Authorities think George Zinkhan's Jeep had been there for days and could have crashed or been stashed there soon after the shootings last Saturday. The professor, an avid hiker, hasn't been seen since he dropped off his two children with a neighbor after the shootings.
More than 200 law enforcement officers searched the dense woods Friday. Helicopters searched from above.
Investigators said Mr. Zinkhan, 57, knows his way around the wilderness, and federal parks officials have warned Appalachian Trail hikers to watch for him.
Authorities said there was little indication he is still in the area near the ravine. Athens-Clarke County Police Capt. Clarence Holeman said authorities believe the vehicle had been there for several days.
Mr. Zinkhan also had a plane ticket to Amsterdam, and authorities in Europe and throughout the U.S. have been on the lookout.
"He's not the typical type of fugitive police have to deal with," said John Bankhead, a spokesman for the Georgia Bureau of Investigation.
FBI Agent Greg Jones said a signal from one of Mr. Zinkhan's cell phones helped lead police to the Jeep in Bogart, a rural town about 10 miles west of Athens, where the professor lived.
Mr. Zinkhan is accused of killing three people, including his wife, Marie Bruce, in front of a theater in Athens. Also killed were Ben Teague, 63, and Tom Tanner, 40, as they gathered for a reunion picnic.
Police hadn't previously revealed a motive, but Agent Jones said Friday that interviews with friends and family indicate Ms. Bruce might have been preparing to file for divorce and the shooting likely stemmed from a domestic dispute between the couple.
Scott Foshee, who lived three doors down from Mr. Zinkhan, said police descended on his suburban neighborhood Friday morning.
"The police had told us there was very little chance he was still around, so we all started to relax," Mr. Foshee said. "And then this morning, it started all over again."