Mitch Snyder, a longtime activist in behalf of homeless people, urged Congress yesterday to allow federal office buildings to be used as emergency shelters and to declare the plight of the homeless a national crisis.

Meanwhile, District officials announced yesterday that city would open up a new emergency shelter Dec. 21 at the old Bundy Elementary School at 429 O St. NW.

Earlier this week, the city was criticized by advocates for the homeless because there had been little progress in opening the shelterthat had been designated as a backup facility when the other three city-run shelters for men and women were full. Advocates predicted this winter would be severe.

Yesterday, the city's medical examiner, Dr. James Luke, said that four of five men who were found dead here since Sunday were apparently homeless. Two of them died from exposure to the cold associated with alcohol intoxication.

One of the men who died of exposure was identified as Don Anthony Clark, 57, whose last known address was 4800 C St. SE.

He was found dead Tuesday afternoon in an abandoned railway warehouse in the 1500 block of Eckington Place NE. On Wednesday, the body of another, James Thomas Rose, 49, of no fixed address, was found in front of a building in the 1600 block of Marion Street NW.

Snyder, a member of the Community for Creater Non-Violence, a Washington group, was among about 40 people at the House subcommittee hearing on homelessness who represented the homeless and public and private shelters from Washington and other large cities.

Snyder claimed that there are as many as half a million homeless people in the country and 10,000 in the District. City officials dispute CCNV's estimates.

In response to Snyder's statements, Audrey Rowe, director of the city's Department of Human Services, held a press conference at the Bundy school during which she said that "There are not thousands of homeless people in the street as some people would have us believe. There is not a crisis. None of our facilities temporary shelters are turning people away."