Agrium urea facility in Borger, TexasTen workers needed hospital treatment on Thursday after leak of anhydrous ammonia at a chemical plant in Borger, Texas.

Fertilizer supplier Agrium Inc. confirmed that an ammonia pump had leaked while being prepared for operations at the plant to restart following several days of repairs. The company evacuated the unit as a precautionary measure.

In all, 13 employees were exposed and 10 were taken to local hospitals for evaluation.

EMS crews from Borger, Stinnett, Fritch, White Deer, Pampa and Panhandle were called in to assist Borger firefighters.

Borger Police Department Lt. Brandon Strope stated that the gas release was contained and posed no danger to the surrounding community. Plant operations personnel were working with the state police, local fire department and regulatory agencies to deem the plant safe and reopen local roads.

Reports on Friday said that authorities were in the process of investigating exactly what had caused the leak, during which time the unit would remain closed.

"Our thoughts are with the injured workers and their families," Agrium said in a statement.

Agrium manufactures and distributes nitrogen, phosphate and potash fertilizers and also supplies specialty fertilizers in North America.

Anhydrous ammonia, a naturally occurring chemical, contains 82 percent nitrogen. It is a liquid when refrigerated and pressurized, but under ambient conditions it is a clear, colorless gas, and a large spill can form a toxic cloud of vapor.