A crash between a car and a Santa Rosa city transit bus Friday morning left four people injured, one with serious injuries.

The Santa Rosa Fire Department was called to the scene on Montgomery Drive just west of Yulupa Avenue around 9:15 a.m. Firefighters spent 25 minutes working to remove the male driver from the car. That driver was taken to Santa Rosa Memorial Hospital with serious injuries, according to a news release.

The bus had nine passengers and a driver on board. All were examined by the fire department and emergency personnel, and two were taken to Memorial Hospital with non-life-threatening injuries, according to fire officials. Another was treated at the scene, said Santa Rosa Police Officer Steve Merical.

The cause was not yet determined, and the investigation is in its early stages, Merical said.

"We are reviewing a video that was retrieved from the bus," Merical said. "I'll be looking at that probably next week."

Tests are being conducted to determine whether drugs or alcohol were a factor, Merical said.

"We couldn't figure it out on the scene, because we had difficulty communicating with the most seriously injured person, who was in the sedan," said Battallion Chief Mark Basque of the Santa Rosa Fire Department.

Basque did not have the name of the injured sedan driver, but said the man was in his late 20s or early 30s. The drivers' records were not yet examined, and Merical was not authorized to release any names, he said.

"Surprisingly, with so many people involved, the scene was very calm," Basque said. "Everybody on the bus was very cooperative."