A patron of the Pavilion at the Old Post Office in downtown Washington received a minor injury yesterday after a glass panel fell from the roof of the historic center and onto a walkway on the ground floor level, according to U.S. General Services Administration officials.

The incident occurred at 2:30 p.m. despite a net placed under the glass roof by GSA after a similar incident occurred 18 months ago. No one was injured that time.

A woman who was hit by a piece of glass received a minor injury to her hand and was not hospitalized, said Dale Bruce, regional director of public affairs for the agency, which maintains the building.

Bruce said the woman left the pavilion without identifying herself. The crowd in the pavilion was small at the time of the accident, he added.

"There is a normal expansion that occurs in the glass and through this expansion the panel let go up there," Bruce said.

He said it was unclear why the net did not prevent the glass from falling to the floor. "Whether the glass from the atrium hit the net, broke there and fell through the net, and then hit the floor, we are not sure," he said.

Bruce said that GSA officials will examine the net to see what improvements will be necessary to prevent a similar accident. Bruce said the glass fell on a walkway near some shops on the south side of the pavilion, which includes restaurants, shops and offices.

Lisa Snead, a leasing representative with the Old Post Office Pavilion Joint Venture, which manages the property, said there was no damage to the area where the glass fell. "Of course, falling glass is dangerous," she added. "We are not really sure what happened."

Bruce said officials believe the glass may have expanded as a result of heat that collects near the ceiling. Because there are hundreds of panes of glass in the ceiling, Bruce said, GSA officials will examine how to improve the net instead of investigating the structure of the ceiling.

"Our emphasis is in the checking and redesigning of the safety net to prevent any further occurrences," Bruce said.