A bus carrying dozens of people crashed and overturned in Delaware, leaving one woman dead and several other people injured, authorities said.

Officials said the accident did not involve other vehicles and happened around 4:20 p.m. Sunday in the community of Bear in the northern part of the state.

Delaware State Police spokesman Sgt. Paul Shavack said there were 50 passengers on the bus when it overturned onto its left side. Shavack said one woman was killed at the scene, and that troopers found her body under the bus.

The 49 others were taken to area hospitals for injuries varying in severity. Of those, three to five people were in critical condition, Shavack said.

Investigators are interviewing the bus driver, who was not critically injured, authorities said.

State police told The News Journal newspaper of Wilmington that there were no apparent witnesses outside the bus to the crash.

But Elvis D'cruz, 19, told The Associated Press that he was driving in the area with a friend when he came upon the overturned bus. He said he and his friend pulled over and were there before first responders arrived.

"Everyone was in pain and crying out for help," said D'cruz, a student at Penn State Brandywine in Pennsylvania.

He said that the group of passengers included largely adults, many of them speaking different languages including Hindi, Mandarin, Spanish and Portuguese.

"There was not one person without blood on them," he said, adding that he and his friend handed out items from a first aid kit.

D'cruz said the bus had overturned on an off-ramp from Delaware's Route 1 that is known for being steep.

New Castle County Department of Public Safety spokesman Sgt. Michael McColley said the crash occurred at Red Lion Road at Route 1 in Bear. It was not immediately clear where the bus was headed or where it began its journey. Shavack said the bus belonged to Am USA Express Incorporated, a bus company based in New York City.

Authorities had no immediate information on the cause of the crash.

Photographs taken at the scene showed the bus lying on the driver's side on a grassy shoulder. The photographs showed at least two people with neck braces lying in the grass while a group of others were sitting nearby.

Video footage taken at the site showed emergency officials leaning over to attend the injured and placing victims on stretchers as ambulances and other emergency vehicles stood by. Debris was scattered about and a ladder had been set up alongside the overturned bus. Later photographs published online showed the bus had been righted.

The National Transportation Safety Board was expected to arrive later Sunday night to open an investigation, police told The News Journal.

Christiana Care Health System spokesman Hiran Ratnayake said 21 passengers were taken to Christiana Hospital in Newark, which has a major trauma center.

Others were taken to other hospitals around the region. Those included another six patients taken to Wilmington Hospital, all of whom were expected to be discharged shortly, Ratnayake said. Six more injured were taken to the Middletown Free-standing Emergency Department, with four of those to be discharged and two of them to be transferred to Christiana Hospital for more extensive treatment.