Authorities have not yet released the identity of the man killed Wednesday night after crashing his Mercedes sedan head-on into a bus on South Bay Boulevard between Los Osos and Morro Bay.

The cause of the crash is being investigated, but witnesses told police the car’s driver, said to be in his 60s, drifted into the southbound lane and collided head-on with the Regional Transit Authority bus about 9:10 p.m. He died on impact.

CHP Officer J.W. Townsen said he was waiting for the county Coroner’s Office to positively identify the man.

Drugs or alcohol are not suspected, but a toxicology test will be done, Townsen said.

The Route 13 bus was on its last trip of the night, headed to Los Osos carrying three passengers.

The woman driving the bus was taken to Sierra Vista Regional Medical Center in San Luis Obispo with injuries and released the same night. Some of the passengers also had minor injuries.

Witnesses said the collision caused the bus to appear to jump into the air before careening down an embankment and into the estuary.

“She did a great job of keeping control of that bus,” said Geoff Straw, RTA executive director. “It could easily have been flipped over.” He would not identify the driver.