Some teen-agers from Indiana on a school trip started a fire that caused $8,000 to $10,000 damage in an Old Town Alexandria hotel room early yesterday when they tossed caigrettes out the window of thir room. Aledandria Fire Marshal Randy Kirby reported.

The teen-agers were in a room on the fourth floor of the old Town Hohday Inn, at 430 King St., and the cigarettes apparently went throuh the window of the hotel room below them, Kirby said.

Three of the teen-agers were treated for smoke inhalation at Alexandria Hospital. Fireman Richard Roomian also was taken to the hospital and treated for cuts on the hospital and treated for cuts on his neck from broken glass, Kirby said. All were released.

A family from San Francisco, vacationing in Alexandria, was asleep in the room where the 2 a.m. fire occurred. Family members were not hurt, Kirby said. About 250 hotel occupants were evacuated.

Kirby said the bus-load of high school students left for Indiana yesterday. He said he is not certain yet whether any charges will be filed in the case. He said the students themselves called the fire department when they saw they had started a fire.