CNN — (CNN) -- A charter bus overturned on an interstate highway in Los Angeles County on Thursday morning, injuring a number of people and bringing traffic to a halt, California Highway Patrol Officer Ed Jacobs said.
The crash happened on eastbound Interstate 210 near the city of Duarte and Interstate 605, nearly 20 miles northeast of downtown Los Angeles.
The number of injured wasn't immediately known. But medical helicopters landed on the highway to transport victims, and numerous emergency personnel were tending to people at the side of the highway, video from CNN affiliate KCAL showed late Thursday morning.
The bus was on its side. At least three lanes of eastbound 210 were closed because of the crash, Jacobs said.