(CNN) — A dust storm caused a 21-vehicle pileup on Interstate 90 in Big Horn County, Montana, on Friday evening, resulting in six fatalities, according to the Montana Highway Patrol.

Montana Attorney General Austin Knudsen said first responders were investigating the accident west of Hardin and that more information will be released when available. Knudsen oversees the highway patrol.

“The Montana Highway Patrol is on the scene with other first responders and investigating the incident,” Knudsen said. “This investigation is still ongoing. We will release more information as it becomes available and is appropriate out of respect of the lives lost and their loved ones.”

Interstate travel was detoured overnight, but I-90 has since reopened, highway patrol said.

“I’m deeply saddened by the news of a mass casualty crash near Hardin. Please join me in prayer to lift up the victims and their loved ones. We’re grateful to our first responders for their service,” Gov. Greg Gianforte tweeted on Friday.

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