DES MOINES, Iowa (AP) _ Chemicals fumes at a hotel pool forced the evacuation of three floors at the downtown Marriott, and as many as 30 people suffering from breathing problems were taken to hospitals.

An employee was mixing muriatic acid, a chemical used to clean pools, with chlorine in a service closet when the mixture caused a cloud of vapor, said Fire Chief Ron Wakeham. He said the vapor cloud was confined to the pool area.

``We're extremely lucky. If this product had been spilled into an open area or down a stairwell, it would have been a high-level situation,'' he said.

Hospital officials said all the patients were conscious and their respiratory problems were being evaluated.

The 415-room hotel was nearly full, with many of the guests in town for the girls' state basketball tournament, said Leigh Murray, hotel marketing manager. Guests on the third floor and below were evacuated. Those above the third floor were asked to stay in their rooms.

A hazardous materials team was working to neutralize the vapors Thursday afternoon. Wakeham said there chemicals could cause lung damage.