Two dozen Catholic University seminarians, bearing signs that asked, "Where is the conscience of the nation," held a vigil outside the Farragut West Metro station in downtown Washington last night and early today, calling on Metro to remove a chain-link gate it built there to keep out the homeless.

Metro erected the gate last week to stop vagrants from sleeping in the entrance and using the area as a toilet at night. The vagrants were causing a public health hazard and disturbing Metro riders and workers alike, Metro officials said.

D.C. police and transit agency officials said that three people were arrested at the station early today. Their identities and the charges could not be learned immediately.

The protesters, members of the Theological College's Social Justice Committee, convened at the 17th Street NW entrance to Farragut West at 4 p.m. after making their weekly rounds ministering to the homeless in alleys, parks and on sidewalks throughout the city. They said the gate had caused anger mingled with a sense of helplessness among Washington street people.

"It's a symbol," said first-year seminarian Stuart Swetland. "It's society saying, 'We don't care.' "

The protesters agreed with Metro and D.C. Department of Human Services officials that subway stations are poor shelters for the homeless, but they said some street people can find no immediate alternative. There is not enough space in the city's shelters, and those left wandering the streets have had difficulty finding warm places to stay, they said.

"We want that fence down. It's not right," Florence Woodward, a 57-year-old homeless person who took shelter at Farragut West last winter, said as she encouraged the students. "I'm fighting but I can't fight by myself."

Woodward, who spent part of last night on a park bench, said the gates could cause serious trouble for people who depended on Farragut West as a haven from the cold.

"It's rough out here when it's snowing. You almost freeze to death," she said.

Shielding candles from the wind, the protesters stood in a circle above the Farragut West escalators and greeted rush-hour passengers with a chorus of "Amazing Grace." An improvised verse urged passers-by to "stop and talk, don't just walk," but few gave the group more than a sidelong glance. And few expressed strong feelings about the fences either way.

Most who were interviewed by a reporter agreed with Anne Walker, a Peace Corps employe, who called the mess left by the homeless objectionable, but feared that they have no place else to go. "There should be another answer," she said.

Some endorsed Metro's action. James McKinney of Herndon, who uses the station every day, said he would start a petition to restore the fence if Metro acceded to the protesters' wishes. "It's just disgusting to have to get off the Metro and have to smell their waste," McKinney said. The vagrants "can find somewhere else to sleep."

Earlier this week, advocate for the homeless Mitch Snyder, leader of the Community for Creative Non-Violence, threatened to tear down the gates if the authorities do not make satisfactory provisions for the street people.

Metro officials said they will meet Monday with advocates for the homeless and Department of Social Services representatives to seek an accommodation, but they said they will not remove the gate. The transit authority's chief obligation is to provide safe, clean, efficient transportation, they said.

"This is not an issue that the transit authority is responsible for resolving," Metro General Manager Carmen E. Turner said Thursday at a Metro board meeting.

Metro is still studying whether gates should be put up at Dupont Circle, Metro Center, Farragut North and McPherson Square, spokeswoman Beverly Silverberg said.