Christmas shoppers at the plush White Flint Mall in Montgomery County were kept at bay for about two hours yesterday as police searched for two young men who apparently tried to do their shopping with a handgun.

Police said two Bloomingdale's employes, who arrived about 9 a.m. to prepare for the 10 a.m. opening, were greeted inside the store's office by two men wearing ski masks. As soon as one of the men displayed a handgun, police said, one employe fled, causing the would-be robbers to panic and flee.

Police said one witness reported seeing two men run from the store's employe entrance and flee by automobile. Just to make sure, however, employes were evacuated from the building and a team of about 15 officers and two police dogs searched nooks and crannies.

They only thing they found, they said, was a handful of mall employes who had hidden out of fear. They found no signs of forced entry into the mall or the Bloomingdale's store, and concluded that the two would-be robbers hid somewhere in the shop before it closed on Sunday and waited overnight.

About 15 other officers guarded possible escape routes, but spent much of their time fending off Christmas shoppers eager to get inside. One police officer, armed with a shotgun and standing behind her cruiser by Bloomingdale's side entrance, provoked little alarm among shoppers. Some shoppers walked in front of her, and seemed puzzled when ordered to stand clear.

"This sets back Christmas shopping," said Doreen Cane, a nanny from Potomac, who leaned on the hood of her Mercedes and waited from 10:30 a.m. until the mall finally opened shortly after noon.

She and her young ward, Stacey, had come to the mall to pick up some stationery and were taking the delay more patiently than some other shoppers. One young woman who pulled into the adjacent parking space swore when told the mall was closed, then drove away.

But most of the customers and store employes -- who said business is normally quiet in the morning anyway -- waited cheerfully, buoyed by occasional arrivals of friends bearing doughnuts and coffee. One seamstress from Bloomingdale's entertained herself by repairing the trouser cuff of a television reporter about to face the cameras.

At the same time the White Flint Mall was being evacuated, police also emptied a building farther north on Rockville Pike after an anonymous bomb threat was made by telephone. Police searched the IBM office building at 1700 Rockville Pike but found no bomb.