A two-alarm fire caused heavy damage yesterday to the Crispus Attucks Museum and Park of the Arts, a former warehouse that was converted to a cultural and recreation center for the neighborhood near Rhode Island Avenue and North Capitol Street.

Two firefighters were injured and an employee was temporarily trapped after the blaze broke out about 4:45 p.m. in the brick building at 69 U St. NW.

The cause of the fire remained under investigation last night, fire officials said. But Richard L. Sowell Jr., executive director of the center, said he was told that several small children may have caused the fire by slipping a burning piece of paper beneath a door.

Fire officials said the blaze spread to the roof of the building before about 70 firefighters, using 28 pieces of equipment, brought it under control about an hour after the first alarm.

Herbert Harpool was in an office in the building when the fire began. "The fire was on me," Harpool said. "It was tremendous. I couldn't get out."

Neighborhood resident Richard Armstead, 33, who was working in his yard when the fire broke out, said Harpool tried to open a door but could not. Armstead said he tore a screen from a window, through which Harpool escaped.

Two firefighters were treated for minor burns at the Washington Hospital Center and were released.

The site was abandoned in the late 1960s by the Chesapeake & Potomac Telephone Co., which gave the property to the District. The city then gave the building to neighboring residents

The building's life as a community center goes back to the mid-1970s. In the mid-1980s, it was bustling with activity, much of it supported by money from the city's Recreation Department. But in 1987, the city cut department funding across the board and the Crispus Attucks staff was pared from eight to two.

This year several neighbors expressed dissatisfaction with the level of activity at the center, although Sowell said at the time that progress was being made toward revitalizing Crispus Attucks.

"We were talking about rebuilding" before the fire, Sowell said yesterday. "Now we have an excuse to go about it in a tenacious manner."