Montgomery County firefighters battled a pair of two-alarm house fires early yesterday, one of which investigators said was caused by arson and resulted in second-degree burns to a 17-year-old girl who may have been injured while trying to save her dog.

The suspicious fire, which caused an estimated $125,000 damage, occurred shortly after 5 a.m. at the home of Kenneth H. and Cornelia Reese at 4612 Hornbeam Dr. in Rockville's Flower Valley subdivision.

Several hours earlier, firefighters put out a blaze at 14447 Taos Ct. in Silver Spring. That fire, which began when a candle ignited curtains in an upstairs bedroom, caused $85,000 damage to the two-story town house, fire officials said.

They said the four occupants of the house, whose names were not released, were alerted when their smoke detector sounded. No injuries were reported.

Officials said firefighters arrived at the Rockville blaze about 5:20. The Reeses' 17-year-old daughter, also named Cornelia, was taken by helicopter to the burn unit at the Washington Hospital Center, where she was listed in fair condition yesterday with second-degree burns on her hands and arms.

Officials said the blaze was set deliberately but did not elaborate.

As workers yesterday afternoon boarded up the house, Kenneth Reese stood in the charred interior, assessing the damage to the family's collection of antique furniture and duck decoys. A certified public accountant whose wife works at a Virginia computer firm, Reese expressed disbelief that the fire could have been deliberately set.

"I can't think of anybody that would do it," he said, standing in the family's den, where a digital clock-radio had stopped at 5:41 and a wall-mounted telephone had melted in the blaze.

Reese, who jumped from a second-story window to escape the blaze, said his wife had fallen asleep watching television downstairs and was awakened by the smell of smoke. He said Cornelia, the only one of the couple's three daughters spending the night at home, hesitated before jumping from her bedroom window.

"We think she may have gotten burned trying to save her dog," said Reese, referring to his daughter's German shepherd that died in the fire.