Residents were evacuated from 50 homes in Clinton yesterday after about 1,000 gallons of acid spilled from a ruptured tank outside a chemical manufacturing building. Prince George's County fire officials said. There were no injuries.

Fire officials said a 3,500-gallon fiberglass tank outside the Chem-Met Co. at 6419 Yochelson Pl. cracked at about 9:30 a.m. and spilled muriatic acid - a mild form of hydrochloric acid - onto the ground and into nearby Peak Hill Creek. Officials called the acid a severe respiratory irritant.

Residents living behind the firm were evacuated after a chemical reaction formed a quarter mile-wide vapor cloud above their houses, officials said. Meanwhile, the creek temporarily was blocked off and powdered limestone poured into it to neutralize the acid.

Nine fire trucks and two ambulances were called to the scene. Most residents were allowed to return to their homes by 11:30 a.m., officials said.

"This was potentially very dangerous and it can be very serious," Capt. John Seanlow said. "In something this big, whether it's gas or oil or acid, there's still a lot of product and it can be very serious," he said.

Residents were calm. "Nobody got over-excited or anything like that. They just took it in stride," said William Taylor. "The only one who got excited was my dog."