About 20 people were enjoying a Christmas Eve dinner in Asmara, an Ethiopian restaurant on Columbia Road NW, when several diners suddenly heard a man crying for help -- seemingly from within the building's walls.

Within minutes, the festive atmosphere turned into a tense rescue drama as firefighters worked to knock out a plywood wall in the restaurant to get to a man who had fallen three stories into a space between buildings.

Firefighters reached the unidentified man about 45 minutes later. He was taken to Washington Hospital Center, where he was reported to be in serious but stable condition last night.

The incident, described as "extremely unusual" by Capt. Kenneth Kavelak of the D.C. Fire Department, began about 8:30 p.m. when diners on the restaurant's second floor heard a man yelling "Help me, help me!"

Some diners peered through a window into the space between the restaurant and an adjacent building, an area about 15 by 20 feet that is about about four feet below the ground level of the restaurant. There, lying on the ground, was a man who apparently had fallen from the roof.

Fire officials who responded determined that the quickest and safest way to get to the man would be to knock out a plywood wall on the restaurant's ground level, because the space could not be reached from the street or the rear of the building.

Restaurant patrons were evacuated from the building, and firefighters used a sledgehammer, hand tools and a hydraulic device called a "jaws of life" to remove the plywood wall, which covered an unused window, Kavelak said.

About 9:15 p.m., rescuers got to the man, put him in a stretcher and took him to the hospital.

Police and fire officials said they did not know why the man had been on the roof.

Tesfamicael Ghebre, owner of the restaurant, said the injured man is a homeless person who frequents the area.

The diners waited in a nearby building during the rescue. When it was over, they walked back to the restaurant, eager to finish their meals.