POTTSVILLE, Pa. (AP) — A collision involving dozens of vehicles on Interstate 81 in Pennsylvania killed at least three people and sent more than a dozen others to area hospitals on Monday, authorities said.

Dr. David J. Moylan, the Schuylkill County coroner, said three fatalities had been confirmed by late afternoon. He said the search of the scene hadn’t been completed because of vehicles still burning. “I suspect it could run higher,” he said.

The Schuylkill County Office of Emergency Management said the crash in northeast Pennsylvania happened around 10:30 a.m. Monday. John Blickley, the agency’s deputy emergency management coordinator, said officials believe a snow squall clouded visibility and likely contributed to the accident.

Estimates of the number of vehicles involved from the emergency management agency and state police ranged between 40 and 60, including multiple tractor trailers. Blickley said emergency personnel from four different counties took about 20 patients to area hospitals for treatment. Three tractor trailers carrying unknown cargo were on fire when emergency personnel arrived and some smaller vehicles were also on fire, he said.

Pennsylvania State Police Trooper David Beohm said Monday afternoon that police hadn’t been able to investigate yet because a fire was still burning among a number of crashed cars and trucks.

“We can’t do anything while there’s still an active fire going,” he said. Fire units on the scene included a steady stream of water tankers because “in the middle of nowhere, you have to bring your own water … there’s not a fire hydrant out here anywhere.”

The highway was snow-covered when the snow squall came through, Boehm said.

“All it takes is one person to crash into something and you have to pull off the road, but when you continue to drive at highway speed, this is what happens,” he said.

People whose vehicles were in the crash and the “walking wounded” were taken to the Wegman’s distribution center in an industrial park near the crash, he said, and a reunification center had been set up at the Goodwill Fire Company in Minersville.

Footage uploaded to social media on Monday showed a tractor-trailer smash into a large dump truck, turning it nearly 180 degrees. Another large truck spewed black smoke and orange flames into the air and an SUV struck a passenger car sending the sedan spinning, narrowly missing its driver who stood on the shoulder of the highway shrouded in snow and fog.

The person who posted the video did not immediately respond to requests seeking additional information. People off camera can be heard yelling as the cascade of crashes unfolds with multiple vehicles colliding in less than a minute.

The National Weather Service had warned of “numerous brief heavy snow squalls with very poor visibility.”

“The squalls will quickly reduce the visibility to under one-half of a mile and coat the roads with snow,” forecasters said, urging drivers to get off the road if possible or turn on hazard lights “and gradually slow down to avoid a chain reaction vehicular accident.”

Mike Colbert, a forecaster with the National Weather Service office in State College, said the weather service started issuing warnings for snow squalls a few years ago, and pileups of the kind being reported were the reason they began doing so.

“They are very heavy snow showers where if you are driving into them, you can go from partly cloudy or sunny skies into an instant blizzard in a matter of seconds. That’s why they are so dangerous,” he said.