A three-alarm fire, believed of suspicious origin, displaced 32 families last night from a Fairfax County garden apartment complex and caused damage estimated at more than $250,000.

The spectacular blaze broke out about 8:15 p.m. in a three-story brick building in the Southern Manor complex, along the Rte. l corridor in the Hybla Valley section of the county. It sent flames leaping 40 feet above the building's roof.

"It was really incredible," said Susan Carlson, a resident of the complex and its recreation director. She said flames poured from third story windows and engulfed the top of the building on Lockheed Blvd. Then she said, there was a popping sound, and a column of flame leaped up from the roof.

The blaze, which brought at least 15 pieces of fire equipment to the development, destroyed three apartments and caused lesser damage to others, authorities reported.

One fire lieutenant estimated damage at at least $250,000, and other estimates ranged to more than $500,000.

Fire department Capt. John Sullivan described the blaze as "definitely of a suspicious nature." Investigators remained on the scene late last night, but as of early today the precise cause of the fire could not be learned.

Firemen, working in a torrential downpour that drenched the area last night, took about one half hour to extinguish the blaze.

No injuries were reported. Red Cross personnel went to the scene to help those who were displaced and vacant apartments in the sprawling 700-unit complex reportedly were made available. Some families said they planned to spend the night with friends or relatives in the area.