HELENA, Mont. (AP) — A 3-year-old and two other children were among the six people killed in a pileup last week on a Montana highway during blackout conditions caused by dust storms, officials said Monday.

Three of the six people who died in the crash just west of the small community of Hardin were children, said Montana Highway Patrol Sgt. Jay Nelson. Officials did not provide the ages of the children except for the toddler.

The pileup happened Friday afternoon after sudden, strong winds with gusts up to 60 mph (97 kph) kicked up dust from farm fields, causing blackout conditions for a mile-long (1.6-kilometer long) stretch of Interstate 90, a major route across the northern United States.

All of the victims were from Montana. The Big Horn County coroner’s office had not made their names, ages and hometowns public by late Monday afternoon.

Nelson also said that 11 people were injured, including three who were hospitalized in critical condition.

There were 29 people in the 21 vehicles from nine states and one Canadian province that crashed and the six people who died were in three different vehicles. The vehicles that crashed included six commercial semi-trucks.

I-90 is the longest U.S. interstate highway in the country, stretching 3,020 miles (4,860 kilometers) from Seattle to Boston.

The crash happened about 50 miles (80 kilometers) east of Montana’s largest city, Billings, during a peak summer traffic hour for people commuting home from work or traveling for outdoor recreation.

The wind that caused the dust storm was ahead of thunderstorms that moved into the area. Nick Vertz, a meteorologist with the National Weather Service in Billings, described it as a surge of wind that kind of appeared out of nowhere.

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