MINNEAPOLIS (AP) _ A chemical supply plant caught fire, spewing chlorine gas into the air early Sunday and prompting authorities to urge residents nearby who could smell the fumes to leave their homes.

Fire officials said people living near the fire at Hawkins Chemical, Inc. should stay put if their doors and windows are already sealed. But they urged people who could smell the fumes to drive _ not walk _ away.

They also sent buses to accommodate the possible evacuation of up to 300 residents in a square-mile area.

A police dispatcher said she had no reports of evacuations in the first two hours after the buses arrived.

The chlorine chemical is similar to those used in swimming pools. The gas causes burning in the eyes and mouth and difficulty breathing, said Deputy Fire Chief Tom Deegan.

``You'd have to get an incredible exposure before it will kill you,'' Deegan said.

The area is part industrial, part residential and includes some campus housing for University of Minnesota students.

Prolonged exposure can cause difficulty breathing and people with asthma are particularly susceptible to its effects, said Dr. Pat Lilja of the Emergency Medical Service, who was at the scene.

Firefighters weren't sure how the blaze started late Saturday night, but suspected it began in a storage room toward the back of the one-story building. It wasn't immediately known if anyone was inside at the time.

Two firefighters were treated for minor exposure and chlorine gas residue was washed off 12 others. Firefighters were letting the blaze, which was contained in the building, to burn itself out because water could cause an explosion or spread the chemicals farther.