POTTSVILLE, Pa. — Tractor-trailers and other vehicles lost control and slammed into each other, people leapt away from careering trucks seconds before collision and at least three people were killed and more than a dozen others injured during a snow squall on a Pennsylvania highway Monday.

The crash on Interstate 81 was captured in videos posted on social media that show drivers and passengers lining the snowy road and jumping out of the way as a cascade of crashes unfolds.

Dr. David J. Moylan, the Schuylkill County coroner, said three fatalities had been confirmed by late afternoon and that number could rise because fires were impeding rescuers.

In one video, an out of control tractor-trailer smashed into a large dump truck turning it nearly 180 degrees, another large truck caught fire and spewed black smoke into the air, and an SUV struck a passenger car sending it spinning narrowly past a person standing on the shoulder in snow and fog.

Video mounted on the dash of a vehicle showed how quickly the road conditions changed. Stopped vehicles rose like a wall in front of the driver, and a person on the roadway stretched their arms out and jumped to escape the runaway vehicle. The impact sounded like thunder.

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 crash.

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 the fires were delaying a full investigation.

Fire units on the scene included a steady stream of water tankers because the crash is “in the middle of nowhere … there’s not a fire hydrant out here anywhere,” Boehm said.

The highway was snow-covered when the snow squall came through, he 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 No. 1 in Minersville for people to meet friends or relatives or arrange accommodations.

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.