Emergency crews responded to a crash involving a vehicle and a bus near Fallbrook, police said.
Shortly after 9:00 p.m. Monday, officials responded to South Mission Road near the River Village Shopping Center after a vehicle struck a Breeze Bus operated by the North County Transit District.
Nine passengers were on the bus at the time of the collision, according to Captain John Choi with the North County Fire Protection District.
Three of the passengers were being treated for minor injuries.
The driver of the vehicle that struck the bus was transported to Palomar Hospital in critical condition after suffering life-threatening injuries.
It is unknown what caused the crash, however, the CHP and San Diego County Sheriff's deputies were going to be investigating the cause of the collision.
South Mission Road between Via Monserate and CA-76 was expected to remain closed for several hours due to a lengthy investigation into the cause of the crash according to Choi.
The bus was serving NCTD Route 306, which provides service between Vista and Fallbrook.