FRESNO, Calif. (AP) _ Malfunctioning chlorination equipment created a chemical cloud over a children's wading pool at a water park, injuring 40 children and an adult who went to help them, authorities said.

One adult and 24 children were treated and released at four hospitals Friday for respiratory ailments, shortness of breath and nausea, hospital officials said. None was admitted.

Others stricken by the gas were treated at the scene and sent home. The park, Wild Water Adventures, is just east of Fresno and about 200 miles north of Los Angeles.

Automatic equipment that disperses chemicals into the wading pool malfunctioned and dumped between a half gallon and a gallon of hydrochloric acid into the water, said Capt. Rich Cornwell of Midvalley Fire Department.

The result was chlorine gas, which can irritate eyes and lungs and cause nausea, particularly in the young or elderly.

''The equipment just put too much in there and formed this gas cloud that overtook people who were in the pool and surrounding area,'' Cornwell said.

Someone hollered, ''Gas 3/8 Gas 3/8'' and children suddenly began having trouble breathing, said Robert Hunter, who had taken his 6-year-old daughter, Amanda, to the water slide resort.

''It evidently dispersed a yellow cloud,'' said Laurel Kopfman of American Ambulance. ''People were running and screaming.'' She added that the children ''were choking, short of breath, vomiting, and some were very sleepy.''

One adult was overcome trying to rescue a stricken child, Kopfman added. Some parents were close to panic after the accident.

Melinda Payton had taken seven children to the pool and admitted later, ''I'm stressed out. ... My 4-year-old came up to me and said he smelled something. Everyone couldn't breathe. They didn't throw up, but they were coughing up mucus.''

The park was crowded with people trying to escape the searing heat that hit the San Joaquin Valley this week. Friday's high reached 112 degrees, which tied a July 5 record set in 1905. Investigators said the extreme heat may have played a part in the equipment breakdown.