At least six people were killed after a dust storm caused between 40 to 60 passenger cars to crash along a major highway in Illinois on Monday, officials said. More than 30 people have been hospitalized because of the pile-up along Interstate 55, which forced emergency officials to close a 30-mile stretch of the road. Multiple tractor-trailers were also involved in the crashes, at least two of which subsequently caught fire, Illinois State Police Captain Ryan Starrick said. Starrick promised that an exact number of fatalities would be provided later on Monday. “Visibility in the area is reported to be low due to blowing dust,” Illinois State Police said earlier in a statement. “Traffic is urged to seek alternate routes. This investigation is in its infancy and there is no further information at this time.” The National Weather Service’s outpost in St. Louis said on Twitter that the dust storm had been generated through a combination of “newly plowed fields & gusty northwest winds.”