08/12/2008 at 05:00 PM EDT
Adrian Grenier and his girlfriend, Transformers 2
star Isabel Lucas, have split on the heels of her car crash
while driving with costar Shia LaBeouf, a source tells PEOPLE.
The pair broke up about three weeks ago, right after the accident that left LaBeouf with a crushed hand. "It wasn't working out," says a source. "Adrian saw her with Shia and that was kind of it – the crash, their hanging out. He obviously didn't appreciate it."
Lucas, 22, was the passenger in LaBeouf's car. She was treated for minor bumps and bruises at the hospital and released.
Lucas's rep confirmed to PEOPLE that the actress "is single."
According to reports, Lucas had been dating Entourage
star Grenier, 32, for several months.
A rep for Grenier wasn't immediately available for comment.
Reporting by JENNIFER GARCIA and MARLA LEHNER