SOMERSET COUNTY, Pa. (WTAJ) — At around 3:40 a.m. on Sunday morning, a tour bus heading from New York to Cincinnati veered off the road onto an embankment and flipped in Westmoreland County.

The bus then rolled back on the road causing a chain reaction with three tractor-trailers and a passenger vehicle crashing into one another.

“It’s the mass of the vehicle right, and then you take the speed and you’re going to get a collision that is more severe than a passenger car,” says Pennsylvania State Police Public Information Officer, Stephen Limani.

All five victims killed were pronounced dead at the scene. Two were U.P.S. drivers and the other three were on the bus, including a nine-year-old girl from Brooklyn.

All 18 patients who were injured and treated at U.P.M.C. Somerset has since been released.

The National Transportation Safety Board has started its investigation into the incident.

“Our role on scene is to document the crash site, document the vehicles that were involved in the crash and then collect the perishable evidence,” says N.T.S.B. Board Member, Jennifer Homendy.