After spending the morning taking in the breathtaking sights at Niagara Falls, a group of tourists boarded a bus to return to New York City, not knowing about an hour later, their bus would be lying on its side in the ditch off the New York State Thruway.

"Avoid the NYS Thruway eastbound at all costs as a tour bus has rolled over near the Erie and Genesee County lines," Erie County executive Mark Poloncarz said on X. "This is a potential mass casualty incident," he said, adding that the county's emergency and security services are assisting.

A rescue operation is underway after a collision involving a tour bus and a semi-truck in Upstate New York on Friday, officials said. The "serious crash" occurred on Interstate 90 in Pembroke, near Buffalo, according to New York State Police. Images from the scene showed the bus on its side and a large emergency response.