Heavily armed D.C. police and FBI agents arrested two suspects yesterday in a holdup of a National Savings and Trust Co. branch at K and20th Streets NW after a nearly four-hour search through nearby office and apartment buildings.

The two suspects were seized in a stairway of the nearby Gwenwood Apartments at 1020 19th St. NW after what police described as a systematic, floor-by-floor sweep through the building. Two other men, picked up by police nearby, were later released and police said they were not considered suspects.

The suspects arrested in the Gwenwood Apartments were later identified as Alan D. Coates, 18, of 1334 Clifton St. NW, and Donald Ray Jewel, 27, of 202 L t, SE. Both were described as unemployed. Police said the two had been charged with armed bank robbery, a federal offense, and would be arraigned todya before a U.S. magistrate.

A third man is wanted in the bank holdup, which took place at about 11:15 a.m. Police refused to say how much money was taken in the robbery, though some of it, they said, was recovered during the search through the Gwenwood Apartments.

The holdup men escaped after the bank robbery, police said, by riding an elevator to the top of the Mercury Building at 1925 K St. NW. Then, police said, they apparently ran across rooftops and jumped to the roof of the nearby, nine-story Gwenwood Apartments.

The incident disrupted traffic and lunch-time business in the area.