A Greyhound bus overturned near Cincinnati early Saturday, injuring 37 people -- including four critically.
The Detroit-bound vehicle was heading north on the I-75 when it crashed near mile marker 26 in Butler County, Ohio, at around 4 a.m., officials said.
Citing the Ohio State Highway Patrol, NBC station WLWT reported the bus drifted off the roadway, first striking a tree and chain link fence, then overturning and sliding to a stop in a cornfield.
Six of the 52 people on board the bus were taken to hospital by air ambulance, according to the Butler County Emergency Operation Center.
WLWT reported that none of the injuries were thought to be life-threatening.
Wendy Parks, director of marketing and communications at Atrium Medical Center in Middletown, Ohio, confirmed that 13 patients were sent there after the crash. Parks said the injuries ranged from moderate to severe.
"The types of injury we saw most commonly were head and neck trauma," she said.
Greyhound spokeswoman Kim Plaskett said that the driver had been on duty for about an hour before the crash.
The bus left Cincinnati at 2:55 a.m. ET and was scheduled to arrive in Detroit at 7:15 a.m. ET, according to Plaskett.
Ohio State Police are investigating the incident.
Butler County is located just north of Cincinnati.