Venancio Leiva was riding the S-2 bus on 16th Street yesterday when it rumbled past the street he lives on. He glanced out the window, and, in that moment, he saw firemen scrambling up an aerial ladder into thick black smoke that was pouring out of his house.

The fire, at 1649 Fuller St. NW, was one of three yesterday that broke out within one hour and a half of each other in a 10-block area of northwest Washington.

The fires left homeless three families who lived at the Fuller Street address; gutted a seven-bedroom boarding house on Girard Street where nine elderly persons and a retarded man lived, and burned through a portion of the second floor of the Manhattan Laundry, which is closed, on Florida Avenue.

No one was badly injured in the blazes, although six persons, including 5-month-old twins from the Fuller Street residence and their 67-year-old grandmother, suffered smoke inhalation and were hospitalized. Novella Goldston, 70, the owner of the Girard Street house was taken to Howard University Hospital because she is a diabetic and needed insulin. A fireman and a policeman were taken to the Washington Hospital Center with minor cuts and smoke inhalation.

Battalion Chief Francis Flaherty said that because the fires occurred in the same locale within such a short timespan, fire officials suspected that arson may have been involved. But he said investigators concluded that there was no connection between the fires and no arson was involved.

After Leiva saw that his house was on fire from his bus window he hurried to the front of the bus, told the bus driver he had to get off, and ran the block and a half to his house.

When he got to his house he saw firemen reaching through the smoke to the top floor of the gray-brick two-story house. There, behind acrid smoke and a closed window, was Sarah Mollina, 67, clutching one of her twin grandchildren to her chest.

Neighbors yelled to the woman to open the window and jump down, but because Mollina is Hispanic and speaks very little English, she did not understand.

Firemen then tried to rescue her by ladder from the front of the house but before they could Battalion Chief Carmel De Blamo ordered his men away from the front of the house. A gas meter, with an open jet of gas, was located under the front porch.

Firemen then went to the rear of the house and broke through the second story window pulling Mollina and her grandchildren from the fire. The elderly woman then collapsed from fright and smoke inhalation, according to fire officials.

One of the twins, Carlos Mollina, also passed out from the heavy smoke that poured through the house. His twin sister, Selia, remained conscious.

Fire officials said five other persons, including four other children, escaped the blaze on their own. The fire was started by an unattended 1-year-old who was playing with matches in a basement closet. His 8-year-old brother turned on a fan in an attempt to put the fire out, fire officials said. The fan spread the smoke through the house and fed the fire, which eventually gutted the first floor and basement of the house.

With the help of a neighbor, who translated the 8-year-old's Spanish to firemen. Victor Hugo, Barrajas, 8, told firemen that he was sleeping in basement when he smelled smoke, woke up, and found his year-old brother. Oscar, playing with matches in the closet.

The boy said his dog had been downstairs with him and he had not seen the dog since the fire broke out at 11:55 a.m.

The Fuller Street fire began while firemen were fighting another blaze 10 blocks away at 1241 Girard St. NW. Fire officials said that blaze began at 11:25 a.m. in a second-story in a bedroom where an elderly woman was sleeping.

Mariam Sile, a niece of the 70-year-old woman who owns the building, said her aunt, Novella Goldston, was talking with two robbery detectives on the first floor of the house when the fire began.

She said the policemen, Bernard Simms and Everett Campbell of the robbery division, helped about five elderly persons out of the house and called firemen to the scene. The policemen were investigating a robbery that took place at the house Monday, Siler said.

The fire burned out the first and second floors of the three-story brown brick house. The Red Cross found rooms in the National Hotel for six of the elderly persons who had lived in the boarding house. The older residents were taken in by their relatives, the Red Cross said.

Janise A. Meade, who lives next to the house where the fire occurred, said that 15 to 17 persons often stayed in the seven-bedroom boarding house. Mead said she moved into the city last March from the Maryland suburbs to "help support our city." She said the elderly persons in the house frequently had trouble with drunks coming into the house and robberies.

Mead's house is a renovated version of the house that was burnt out yesterday. Mead said she has repeatedly called city officials in attempts to get the neighbors to clean up their backyardvbnd the area in front of the house.

Yesterday's third fire occurred at the Manhattan Laundry at 1330 Florida Ave. NW. According to fire officials the fire began at 1 p.m. in the vacant building and burned through a portion of the flooring between the first and second stories before firemen broke down a door to get into the building.