The charred bodies of three small children were found early today on the second floor of a row house in Northwest Washington's inner city after a fierce and smoky fire broke out there.

Fire investigators said early this morning that they did not know the cause of the fire but that they were looking into the possibility of arson. Possible witnesses were being interviewed by police homicide detectives.

At least two of the children were found in a second-floor bedroom of the two-story brick and stone row house at 214 Morgan St., a one-block-long street of deteriorating structures near the intersection of New York and New Jersey avenues.

Searing flames and billowing smoke engulfed the room in which the children were found, and when firemen were finally able to enter they found the bodies amid heaps of smoldering debris.

All three children were described as 4 years or younger. Their precise ages were not known, and they could not be immediatley identified. Authorities were interveiwing a woman they said was the children's mother.

Fire officials said an alarm was received about 1 a.m. and firefighters, who reached the scene within a minute or two, reported flames and thick smoke issuing from the second floor. In all six engine companies were sent.

Authorities said the fire was under control within 15 minutes after the firefighters arrived.