(CNN) — A parade of ambulances snaked down a narrow, two-lane highway Sunday night, waiting to transport the dozens injured from a fatal tour bus crash in Southern California.
The mountainous terrain hampered rescue efforts in San Bernardino, east of Los Angeles, as authorities tried to extricate some of the victims.
The San Bernardino County Fire Department said multiple people were killed, but could not pinpoint an exact number.
The bus rolled over and crashed about 6:30 p.m. (9:30 p.m. ET) in a mountainous area of State Route 38 in San Bernardino, said Eric Sherwin, a Fire Department spokesman.
At least 27 people were suffered injuries ranging from minor to severe, Sherwin said.
The highway was reduced to one lane for both inbound and outbound ambulances, which had to contend with a downhill grade and winding roads.
The cause of the crash was not immediately known.