A three-alarm fire swept through the Woodbridge Apartments yesterday morning, gutting at least two of the units and displacing 40 residents, according to Prince William County fire officials. They estimated damage at $200,000.

There were no deaths or serious injuries in the blaze, and four firefighters suffering from smoke inhalation and dehydration were treated and released from Potomac Hospital in Woodbridge, officials said.

The fire was started shortly after 9 a.m. by a two-year-old boy playing with a cigarette lighter in a second-floor apartment, officials said. The child's mother pulled him away from the blaze, which started in a mattress and quickly spread through the apartment, burning through the ceiling and into the apartment above, officials said.

The other nine units in the three-story brick building, located at 1903 Stevens Rd., Woodbridge, suffered varying degrees of smoke and water damage. Apartments on the north side of the building, where the fire started, were most heavily damaged, officials said.

Firefighters responding to the alarms found flames licking from the windows and plumes of smoke mushrooming high into the pale blue morning sky. The thick smoke was visible for several miles.

Fourteen units from Prince William and Fairfax counties and Quantico responded to the three alarms, and the blaze was under control by 11 a.m., officials said.

Red Cross volunteers were on the scene for most of the day, locating temporary shelter for the 11 displaced families. Officials said some would be able to reoccupy their apartments within days.