At least 35 employees of a company in Jurupa Valley were overcome Friday by an odor of an unknown substance.
A call was received around 7:45 p.m. from Swift Transportation at 11888 Mission Blvd., according to an incident report from the Riverside County Fire Department.
About 40 firefighters along with hazmat teams and environmental health officials responded to the location.
Aerial video from the scene showed several people being decontaminated and then loaded into ambulances.
At least 19 employees were transported to the hospital by ground ambulance around 10 p.m., fire officials said.
Ten other patients were taken to the hospital by a Riverside Transit Authority (RTA) bus.
At 11 p.m. officials said an additional 6 employees had been affected and would be transported to an area hospital by a second RTA bus.