Update 8:30 a.m. Saturday, 7/16:
Six people are confirmed dead and eight people were transported to nearby hospitals, after a 21-vehicle pileup being described as the one of the most intense multi-vehicle accidents to occur in Montana.
Montana Highway Patrol Sgt. Jay Nelson says the numbers of fatalities and injuries did not change over night and the accident scene has been totally cleared.
Sgt. Nelson says information so far points to the conditions of the wind storm that caused the accident as an isolated, extreme weather event and they do not believe there is any further danger to the public.
Sgt. Nelson says accident investigators are combing through all evidence and should have a thorough accident report on Monday, when the coroner is expected to make a statement as well.
"In my 24 years of experience, this is one of the most intense multi-vehicle accidents we've had in the state of Montana," Sgt. Nelson said.
He says with the intense wind and dust, it was tragedy in an instant.
Update 8:50 p.m.
At least five people are dead following a pileup of more than 20 vehicles on I90 near Hardin Friday evening, according to the Montana Highway Patrol.
Authorities are continuing to sift through the wreckage and expect the eastbound traffic to continue to be diverted until midnight or later.
The death toll could rise, and troopers did not say how many were injured.
Eyewitnesses said the area was cloudy and dusty with low visibility shortly after the crash was reported around 4:30 p.m. Friday.
“It was like a snowstorm but dust it was very low visibility, it was like fog. It reminded me of very dense fog," motorist Ariel Dehart told MTN News.
Troopers remain at the beginning stages of the investigation of the causes of the crash and remain uncertain where it started.
This is a developing story. Check back for updates.
Update 8:10 p.m.
Motorists told MTN News that visibility around the crash scene on I90 near Hardin was bad, as was the carnage.
“As we got closer into the dust storm, you could start seeing the vehicles in the ditch. There was a camper, the whole side of it was blown off, the top was off of it. Front ends of vehicles were smashed in," said motorist Landa Uffelman.
Others said dust obscured the view of the scene from outside of 10 feet. A storm had pushed through the area not long before the pileup was reported.
“We couldn’t even see like 10 feet in front of us so we immediately hit our brakes. On both sides, there were cars braked and stopped, and then I saw a van that was just pancaked into the back of a semi. And then behind it, there were about 20-30 vehicles that were piling up on each other," said Tom Howe, who had passed through the scene.
Sheyenne Scheeler, who snapped several photos of the scene, said she saw several cars that were crushed. She called the incident "gut wrenching."
“The first thing that we saw was a pickup that had been pulling a camper and the camper looked like it had been ripped open like a can. And then after that we started seeing more cars that had rear ended," she said.
Montana Highway Patrol troopers are expected to release an update on the crash later Friday night.
(first report) At least 20 vehicles crashed in the westbound lane of Interstate 90 three miles west of Hardin Friday evening in what authorities are calling a "mass casualty incident."
Montana Highway Patrol Sgt. Jay Nelson told MTN News that the incident was reported around 4:30 p.m. and first responders were still arriving to the scene 90 minutes later.
The crash is centered around mile marker 493 near Hardin.
Motorists should expect delays in the area. Authorities are expected to be at the scene for several hours.
This is a developing story. Check back for details.