Under the big fluorescent lights, the two truck drivers who had pulled into Rosemount from Oklahoma seemed to be having trouble with a connection in the piping that one would use to pump the anhydrous ammonia into his semitrailer truck.

Witnesses said there were noises, then a bang, and the escape of invisible but deadly anhydrous ammonia that killed one driver and critically injured the other Monday evening.

Police and another truck driver dragged one trucker from the immediate area of the vapors, which had been dissipating into the nearby woods, and began cutting his soaked clothing off of him.

That man, Roy Thomas Taylor, 56, of Moore, Okla., was airlifted to Regions Hospital, where the officers also were treated and released with throat irritation. Taylor remained in critical condition Tuesday night.

Killed was Robert Shue, 31, of Kingfisher, Okla.

Taylor and Shue were working for a trucking firm that specializes in carrying hazardous materials, High Pressure Transports, which is based in Kingfisher.

"We don't know what happened, but we hope to find out," said Brian Spencer, general manager for distribution facilities for CF Industries, where the accident occurred. Federal and state officials have yet to rule on the cause of the accident.

"Statements from the drivers indicate there was some problem with the connection," Spencer said of the steel piping and connector that is used to pump the fertilizer ingredient into truck tanks.

Located on the Mississippi River, CF is surrounded by black railroad tankers used to carry the product, the most efficient fertilizer available for cornfields. The fertilizer manufacturer also uses barges to distribute the fertilizer.

The company is a subsidiary of CF Industries Holdings Inc., one of North America's largest manufacturers and distributors of nitrogen and phosphate fertilizer products. Ammonia is used in fertilizer because of its high nitrogen content, but it can be deadly, and its use and transport are regulated.

Company officials and workers, law enforcement officers who were on the scene, and others described a deadly leak that lasted only a few seconds before it blew away.

Monday, the trucks were lining up during the height of the fall fertilizer season for farmers. The fertilizer-maker had been running around the clock when two truckers from Oklahoma drove down Pine Bend Trail to get in line just before 6 p.m.

Trucks were pulling single file into a scale house to be weighed and inspected. Taylor and Shue pulled their trucks up to a loading station -- an 8-by-16-inch enclosure surrounded by metal piping and valves.

Hanging nearby, and connected to a tank, are a couple of reticulated steel pipes with swivels in them, each like the arm on a dentist's giant lamp. They carry ammonia pressurized at 190 pounds per square inch.

Dean Hicks, a 21-year CF employee, on Tuesday told of hearing a loud bang, looking up to see a white vapor cloud and hitting the big red dome button that shuts down everything in the plant.

Hicks ran out to a man who was incoherent and poisoned, but Hicks could not get him to his feet. He wanted to wash him off. Nearby were troughs of water. But unable to get him up, Hicks ran to get help.

Rosemount police officer Scott Sandell heard the call at 5:58 p.m. and arrived within three or four minutes.

On his heels was Dakota County Deputy Matt Schuster.

The area around Shue, the man who died, was still toxic, Schuster and Sandell said.

"There was residual in the air. We couldn't get to him," Sandell said.

That man lay by the front of his truck as the two officers talked quickly. Then, joined by a trucker who was on the scene, they grabbed Taylor and pulled him to safety.

Joy Powell • 952-882-9017