At least four people have been killed, including a child, and dozens injured after a tour bus overturned on the highway in upstate New York this afternoon.

Rescue operations are underway at the 'mass casualty' rollover crash along I-90 in Pembroke, near Buffalo.

The bus, believed to have been traveling from Niagara Falls to New York City, had at least 52 people on board, WROC reports. Several people are dead, trapped and injured.

Photographs from the scene show the bus turned over on its side and a heavy police presence along the highway.

Multiple emergency medical helicopters have responded to the scene.