Five people died and dozens were injured in a "horrible" crash involving a tour bus and three tractor trailers on a major US highway Sunday.

Pennsylvania State Police said the pre-dawn crash on the busy Pennsylvania Turnpike - billed as America's "First Superhighway" - happened at about 3:40 am (0840 GMT) in Westmoreland County, east of Pittsburgh. "There are five fatalities," the police said on Twitter, adding that 39 people were taken to hospitals. But Turnpike spokesman Carl DeFebo said "probably dozens of patients, about 60 patients" were transported to local hospitals after the "horrible crash." "I personally haven't witnessed a crash of this magnitude in 20 years," he told Pittsburgh's Action 4 News. Aerial images broadcast by the station showed a bus overturned.