Three passengers have died after a charter bus carrying up to 50 people collided with a vehicle on a major road in the US state of Pennsylvania, police said.

The crash happened during heavy rain at about 11.50pm local time on Sunday (4.50am on Monday BST) on the southbound Interstate 81 in Dauphin County’s Lower Paxton Township, near Harrisburg, Pennsylvania State Police said.

The bus struck an embankment before hitting the rear end of a car and flipping on its side.

“Three passengers were declared deceased on scene,” the police report said. Others passengers had injuries ranging from minor to severe.

“This is considered a mass casualty incident,” Trooper Megan Frazer said. “We do have eight ambulances that assisted with us, as well as lifeline (emergency response), just because of how many people were involved and the amount of injuries.”

It was raining heavily at the time of the crash, WHTM-TV reported Frazer said.

Multiple people were taken to Milton S Hershey Medical Centre with injuries.

The American Red Cross of Greater Pennsylvania was providing food, drinks and cots at the Chambers Hill Fire Department for passengers being discharged from the hospital.

When asked how many people were being assisted, the Red Cross said “the situation is still evolving” and they were not able to release a number.