Toxicology tests showed Steven Culbertson, 19, of Petaluma, did not have any alcohol in his system at the time of the 9:20 p.m. collision at the Intersection of Highway 37 and Lakeville Road on Nov. 28, CHP Officer Jonathan Sloat said.
Further toxicology tests are being done to rule out prescription and hospital administered medication, Sloat said.
John Maloney, 45, his wife Susan, 42, and their children Aiden, 8, and Grace, 5, were killed when Culbertson drove through a red light and collided with the family's 2004 Nissan Quest, the CHP said.
The CHP and the California Department of Alcoholic Beverage Control investigated a report that Culbertson was seen drinking alcohol in the Traxx bar and restaurant in Petaluma before the crash. Sloat said that claim could not be substantiated.
"Based on other witnesses, as well as cell phone records, investigators were unable to confirm that Culbertson was at the bar or his Mini Cooper had been in the parking lot of the bar," Sloat said in a statement.
The CHP is still investigating the crash but it appears Culbertson drove through a red light at the intersection, Sloat said.