Nineteen soldiers were taken to an Army hospital Wednesday after they were exposed to fumes while cleaning a training area at Fort Bliss.

Post officials said the soldiers from the 31st ADA Brigade (search) reported breathing problems as they were cleaning out a large metal storage box in the training area.

Water apparently reacted with a powder in the container and created a noxious cloud. The powder was a concentrated form of a chemical used to purify water, though it was unclear exactly which chemical, said post spokeswoman Jean Offutt.

About a dozen soldiers treated at the hospital were released within a few hours. The condition of the those still hospitalized wasn't immediately released.

Hazardous materials experts from Fort Bliss (search) and the El Paso Fire Department were called after the soldiers became ill.

Fort Bliss, near El Paso, has about 12,000 soldiers.