Six people were killed after a sandstorm fueled by wind gusts of more than 60 mph caused a jam Friday night on Interstate 90 in Montana, authorities said.
Twenty-one vehicles collided, and Montana Highway Patrol Sgt. Jay Nelson said authorities believe the weather was a factor.
“It looks like there was a strong wind blowing, causing a sandstorm with zero visibility,” he said.
Although the highway patrol did not immediately count the number of injuries, Nelson said additional ambulances had to be called from Billings to assist.
Gov. Greg Gianforte said on Twitter: “Deeply saddened by the news of the mass casualty near Hardin. Please join me in praying that we lift up the victims and their loved ones. We are grateful to our first responders for their service.”
Montana Attorney General Austin Knudsen, who oversees the highway patrol, said in a statement: “The Montana Highway Patrol is on scene with other emergency responders investigating the incident. We will release more information as it becomes available and appropriate out of respect for the lives lost and their loved ones.
“My prayers are with everyone affected by the tragic events of the Big Horn County dust storm today,” Knudsen added.
The incident occurred 3 miles (5 kilometers) west of Hardin. Video from The Billings Gazette showed hundreds of tractor-trailers, campers and cars backed up for miles along the two eastbound lanes of the interstate.
The sandstorm’s roots can be traced back several hours, when storms formed in south-central Montana between 1 and 2 p.m. and slowly began to move eastward, according to Nick Vertz, a meteorologist with the National Weather Service in Billings.
Those storms prompted a severe thunderstorm watch to blanket Hardin and other parts of Montana from mid-afternoon to 9 p.m. Friday. Meteorologists forecast the possibility of isolated hail the size of a quarter, wind gusts of up to 75 mph (121 km/h) in places and frequent lightning.
The so-called “spout” — or wave of wind produced by storms but can travel faster than them — was flying east/southeast about 30 miles (48 kilometers) ahead of the storms, Vertz said.
A wind gust of 40 mph (64 km/h) was reported at the nearby Big Horn County Airport at 4:15 p.m. The accident was reported to the Highway Patrol at 4:28 p.m.
By the next reading of the weather station at the airport at 16:35, wind gusts had increased to 100 km/h. A second reading 20 minutes later recorded an impact of 103 km/h.
Winds easily whipped up the dust — a product of recent temperatures in the 90s and triple digits over the past week — and reduced visibility to less than 1/4 mile (0.4 kilometers).
“If they looked up at the sky when they were in Hardin, they probably didn’t see much of what you would think of a thundercloud, maybe not much at all,” Vertz said. “It was just a gust of wind that came out of nowhere.”
As first responders try to remove the wreckage, the meteorologist said they can expect to be safe from additional winds and thunderstorms.
“It should be a relatively clear, calm night for them,” he said.