Part of a California interstate highway was closed Sunday after an accident killed at least three people and five others were taken for medical treatment.

The crash happened eastbound on the 10 Freeway in Riverside County around 7:30 a.m. local time, according to the Riverside County Fire Department. It is not clear what caused the accident, but the road is expected to be closed for a minimum of two hours.

Three people were pronounced dead at the scene of the accident, the fire department said.

Two others were airlifted to a trauma center with serious injuries, while three people with moderate injuries were transported to the hospital.