PUEBLO, Colo. (AP) — Four people died in crashes involving over 30 vehicles, including six semitrailers, on an interstate in Colorado Tuesday after blowing dirt made it nearly impossible to see, authorities said.

Dirt kicked up by heavy winds blew across Interstate 25 just south of Pueblo around 10 a.m. causing a “brown out,” Maj. Brian Lyons of the Colorado State Patrol said.

“Visibility was next to nothing,” he said.

Twenty-nine people were taken to the hospital with injuries ranging from minor to severe, Lyons said. There were crashes on either side of the interstate, but the one on the southbound side only led to property damage, the patrol said.

One of the vehicles was a pickup hauling a trailer carrying 32 goats, four of which died, the patrol said.

The cause of the crashes about 2 miles (3.2 kilometers) from Pueblo is still being investigated. The lack of visibility will be considered as one of the factors, but others may also be involved, said Trooper Sherri Mendez, a patrol spokesperson.

The strong winds that hit the eastern half of Colorado on Tuesday, combined with warm weather and very dry conditions, were also blamed for fanning wildfires and causing flight delays at Denver’s airport.

Meanwhile it snowed in the western part of the state, bringing much-needed moisture to the mountains.