Three children were killed and their mother critically injured in a fire yesterday morning that destroyed their Hagerstown, Md., row house, damaged two adjoining homes and injured nearly a dozen firefighters, Hagerstown fire officials said.

Wilbur R. Poffenberger Jr., 8, his sister, Tracy Lynn, 11, and their brother Garrett, 7, were pronounced dead on arrival at Washington County Hospital, fire officials said. Their mother, Doris Jane Poffenberger, 31, remained in critical condition last night at the Baltimore Regional Burn Center at Francis Scott Key Hospital in Baltimore.

The children's father, Wilbur R. Poffenberger, was at work at the time of the fire, authorities said.

According to Hagerstown Fire Battalion Chief Kingsley Poole, the house at 829 South Potomac St. was already fully ablaze when the first firefighters arrived at 7 a.m. Flames were visible from the front second-story windows -- the area where the three children were found -- and Poole said it was believed the children were already dead when the alarm was received.

Doris Poffenberger was found unconscious in the kitchen on the first floor, which also was filled with heavy smoke and flames. She was taken to Washington County Hospital before being transferred to the Baltimore burn center.

The nearly eight-hour struggle to control the fire involved four engine companies, two ladder trucks, four medical units and the Washington County Air Unit. One firefighter was admitted to Washington County Hospital with a broken back, two were treated for heat exhaustion and lacerations and released, and eight others were treated at the scene for minor burns and smoke inhalation, Poole said.

Although the houses at 825 and 827 South Potomac St. also were damaged by the blaze, the residents at those addresses were warned by smoke alarms and escaped injury. It was not immediately known whether the house that the Poffenbergers rented was equipped with a smoke detector.

"It was a really hard fire to fight because they're what we call 'balloon-frame construction' " row houses, Poole said. "There's no fire stoppage in the walls from basement to roof . . . and there's a common loft area over all three." Poole described the row houses as being in an older, middle-class neighborhood.

Yesterday's tragedy came barely a day after three Washington residents were killed in a fire in Northeast, and less than two months after a man and five children died in a fire at a foster home in Southeast.

Poole said yesterday that the three deaths were the most in one fire in his memory. "I've been with [the department] 24 years," Poole said, "and I only ever remember two at once."

However, Poole said, "there's something ironic about it happening right there. Two people were killed in 1977 in a fire in the house straight across the alley -- and that was my fire, too."