(CNN) -- A charter bus bound for a casino overturned on an interstate highway in Los Angeles County on Thursday morning, injuring 46 people, officials said.
Most of the injuries were minor to moderate, Saul Gomez of the California Highway Patrol told CNN. Several trauma patients were airlifted by helicopter.
"Luckily, none are life-threatening, and the situation has stabilized for now," Gomez said.
Witnesses were still being interviewed, and it was too early to ascertain a cause of the wreck, he said.
The bus, which was on its side off of Interstate 210 near Irwindale, had traversed four lanes before coming to rest. The stretch of highway is popular with tour buses headed to casinos. The wreck occurred at about 10 a.m. (1 p.m. ET)
The crash happened on eastbound I-210 near the intersection with Interstate 605, nearly 20 miles northeast of downtown Los Angeles. By early afternoon, one eastbound lane of I-210 was open.
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.
Pasadena's Huntington Hospital had three patients, including an 86-year-old man with chest injuries and rib fractures, hospital spokesman Kevin Andrus said.
Three hospitals in the Citrus Valley Health Partners system had a total of 20 patients, all of whom were listed in mild to moderate conditions, spokeswoman Annette Macias said.
CNN's Phil Gast contributed to this report.