Athens-Clarke police said in a statement that they found George Zinkhan's vehicle overnight in the northwestern part of Clarke County, the same county where the university is located.
Police have not yet found Zinkhan, who was last seen driving away in a red Jeep after dropping his children off with a neighbor. They were in his car during the shooting but weren't hurt.
Authorities across the nation and in Europe have been searching for the 57-year-old business school professor, who was fired after the April 25 shootings.
The university is warning students to be cautious until he's found.
Killed were Zinkhan's wife, 47-year-old attorney Marie Bruce, and two members of her community theater group, Ben Teague, 63, and Tom Tanner, 40. Authorities have not released a motive.
They revealed earlier this week that Zinkhan had a flight to Amsterdam booked for Saturday and they had found an empty passport wallet at his house. Zinkhan has taught part-time at the Vrije Universiteit (Free University) in the Netherlands since April 2007.
Zinkhan's brother said earlier this week that his relatives have been working to help Athens-Clarke County police and the FBI find him.