Two women were killed and nearly 50 others were hospitalized after a bus carrying passengers returning from a sightseeing tour of Washington D.C. overturned in Delaware Sunday. 

Officials said the accident did not involve other vehicles and happened at around 4:20 p.m. local time on State Route 1 in New Castle in the northern part of Delaware, south of Wilmington.

Delaware State Police spokesman Sgt. Paul Shavack said the bus was going through a curve when it left the road and overturned. The bus slid on its roof down a grass embankment and came to rest on its left side.

In a later statement, Shavack identified the victims as 54-year-old Hua'y Chen, of New York City and 30-year-old Idil Bahsi of Istanbul, Turkey. The statement said Chen was pronounced dead at the scene, while Bahsi was pronounced dead at a local hospital late Sunday. All 47 other passengers were also hospitalized with various injuries. 

Authorities said investigators were interviewing the bus driver, 56-year-old Jinli Zhao, who was not critically injured.  Shavack said the bus belonged to Am USA Express Incorporated, a bus company based in New York.  Investigators said the passengers were returning to New York after a weekend in the nation's capital. 

Elvis D'cruz, 19, told The Associated Press 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 the group of passengers included mostly 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 that is known for being steep.

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 open an investigation, police told The News Journal of Wilmington.

The Associated Press contributed to this report.