One truck driver was killed and another was critically hurt when anhydrous ammonia was released Monday night in Rosemount.

A Rosemount police officer and a Dakota County sheriff’s deputy also were taken to Regions Hospital in St. Paul to be checked out, Rosemount police Sgt. Bryan Burkhalter said. The release happened about 6 p.m. during loading at the CF Industries ammonia terminal at 13040 Pine Bend Trail.

Authorities are still investigating the cause of the release, but they believe a hose from one of the trucks came off or ruptured. “I don’t think it was a lot because a plant employee shut it down immediately,” said Burkhalter, adding that the ammonia immediately dissipated.

Law enforcement and company officials believed the facility, in an industrial area with no homes nearby, was safe Monday night. It is near the Mississippi River and where Hwys. 55 and 52 separate in Rosemount.

“Everything is shut down right now,” said Terry Huch of CF Industries.

One of the drivers was dead on the scene and the other was flown by medical helicopter to Regions, he said. Both truckers were from Oklahoma, Rosemount police said. The exact nature of the injuries were not known, the company said. Huch said no other information about the drivers was being released Monday night.

The Dakota County medical examiner’s office was still at the scene Monday night, and investigators from the state Occupational Safety and Health Division were expected to take over Tuesday, Burkhalter added. Rosemount firefighters, the State Patrol, HealthEast Ambulance and North Air Ambulance also responded.

CF Industries is cooperating with local officials and have started an investigation as well, a statement from the Deerfield, Ill., company said. The facility is one of two in the area belonging to CF Industries, said Huch, senior director of investor relations and corporate communications.

The one where the release happened is a terminal that deals with anhydrous ammonia, the most concentrated nitrogen fertilizer, according to the company’s website. It receives the ammonia via barge and rail and ships it to customers via truck.

Burkhalter said the facility had up to six loading stations. In 2008, Minnesota reported three workplace deaths as a result of exposure to harmful substances or environments, according to the state Department of Labor and Industry. Drivers accounted for nine of the 65 workers with fatal injuries last year.