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A body is covered with a blanket at the scene.

The limousine landed in the woods following the crash.

Debris covers an area at the site of the fatal crash in Schoharie, N.Y.

Twenty people were killed when a limo heading to a surprise birthday party crashed in upstate New York, relatives and reports said Sunday.

Eighteen of the dead were in the stretch SUV limo, while two were bystanders, authorities said. The group was going to a surprise birthday party, a relative of one of the victims told The Post.

The limo failed to stop at an intersection and careened into an empty parked car in a restaurant parking lot in Schoharie, about 35 miles west of Albany, around 1:55 p.m. Saturday, authorities said. The struck car was pushed into two pedestrians, killing them, while the limo barreled into a small ravine, killing everyone in the vehicle, including the driver, officials said.

The limo was speeding when it smashed, witnesses said.

“I heard a loud bang, [and] I came out my front door to see what was going on,” resident Bridey Finnagen told local ABC affiliate News 10. “I saw a lot of people here at the Apple Barrel out in the parking lot. Then I heard screaming.

“Then I saw this large van, a very unusual-looking vehicle out here in Schoharie, in the bushes and really wrecked, hit a tree,” she continued.

The crash kicked off a huge emergency response that included six ambulances, three fire companies and two helicopters, the Times Union reported.

“The first responders broke some windows [on the vehicles] to try to get people out,” said Finnegan. “I believe the Jaws of Life were here on the side of one of the fire trucks.”

State police confirmed the deaths of 20 people at the scene, but would not provide any other details pending a 3 p.m. news conference.

The names of the deceased were not immediately released as state police worked through notifying their next of kin in the wake of the massive smash-up.

Investigators from the National Transportation Safety Board were en route to investigate one of the deadliest vehicular accidents the region has seen in years.

Those fearing that a loved one may have been involved in the collision are urged to call the New York State Police at (877) 672-4911.