A waiter was shot and seriously injured yesterday afternoon during an apparent robbery attempt at a Georgetown pizza parlor that had just opened its doors for the day.

The 28-year-old waiter, William Wendell, of the 1200 block of Girard Street NW, was taken to Georgetown University Hospital suffering from a single gunshot wound to the abdomen. He was undergoing an operation last night and was listed in serious condition.

D.C. police, sporting flack jackets and rifles, cordoned off a two-block area in busy Georgetown to conduct a search of the three-story building at 3211 M St. NW that houses Uno Pizzeria. But police said they were unable to find either of the two men who allegedly tried to rob the restaurant around noon yesterday.

The incident began when a man came through the front door of Uno's and ordered two customers and eight restaurant employes to lie face down on the floor, said D.C. police Lt. Hiram Brewton.

Uno manager Art Brumer said the man, whose face was hidden by a ski mask, ordered those inside to "Hit the deck," then went to the back of the restaurant, opened a rear door and let a companion in. Brumer said the injured waiter was coming down a stairway into the restaurant and apparently did not hear the order to lie down. He encountered the two men as they returned from the rear of the restaurant, and one of them fired a shot at him, Brumer said.

Police believe that only one of the two men was armed.

Officers said they believe the incident was a robbery attempt even though no money was demanded or taken. The two men apparently fled from the rear of the restaurant as soon as the shot was fired, Brumer said.

Police making a routine patrol on M Street were alerted by the noise and quickly took one man found outside the restaurant into custody. He was held briefly for questioning but released late yesterday afternoon.

Police searched the area for about two hours but failed to find either man.