Authorities say a tour bus returning to New York City from Niagara Falls has crashed on an interstate highway, killing five passengers and injuring many others.

"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.