Evacuations were under way early this morning in the neighborhood of a plant center in upper Montomery County while a two-alarm fire blazed through a building where chemicals are stored.

After several firefighters were overcome by the fumes, authorities said they would evacuate the area for a half mile around the Brookville Plant Farms at 3901 Gregg Rd. in Brookeville.

Authorities indicated that as many as 50 persons might be evacuated.

County fire officials said that the blaze, which began late last night, destroyed three buildings at the plant farm. The fire at the fourth building, which contained the chemicals, was still blazing shortly before 2 a.m. today.

The cause of the blaze was not immediately known and no dollar value for the damage could be learned last night.

The three buildings destroyed were described as barn-like in structure. The chemicals in the forth building were belived last night to be pesticides used in agriculture.

Firefighters were at the scene of the blaze, near the intersection of Gregg Road and New Hampshire Avenue, before the fire appeared to spread to the building in which the chemicals were kept. About 12:30 a.m. today, five or six firefighters showed symptoms of exposure to fumes and were taken to Montgomery General Hospital.