WESTPORT, N.Y. — State police said several passengers were killed and numerous others were injured when a Greyhound bus heading to Montreal from New York City on the Northway crashed through a guard rail and landed upside down in an embankment yesterday.

State police believe up to five people are dead, Trooper Ryan Bentley of the Westport barracks said.

At least 20 passengers were lying on blankets and stretchers while receiving care from medical personnel. The back and top of the bus was crushed and one of its back wheels was turned inward.

A former mayor, Daniel Stewart, and his partner, Jon Recor, were among the first people at the crash site, the Plattsburgh Press Republican reported from the scene. Mr. Steward provided a blanket to cover some of deceased.

The bus, No. 4014, departed New York at 1 p.m. and made stops in Albany and Saratoga Springs before the crash, a Greyhound spokeswoman, Anna Folmnsbee, said. There were 52 passengers and one driver onboard, she said. It was traveling northbound on Interstate 87 at about 6:45 p.m. when it overturned just before exit 31 near Elizabethtown.

The injured were taken to hospitals in Elizabethtown, Plattsburgh, and Glens Falls. CVPH Medical Center in Plattsburgh was in disaster mode and called City Police Department for help with crowd control.

A spokesman for Champlain Valley Physicians Hospital Medical Center in Plattsburgh, Mike Hildebran, said 25 people had been treated there as of 10:30 p.m. and several more were en route. The patients were of all ages, including a few children.