Smoke from a cozy fireplace set off a fire alarm in Pforzheimer House's Jordan Hall Sunday night.

The flue was open when the people in the room started the fire, said Glen R. Magid, a resident tutor in Jorden who was in the room at the time.

"Before we started the fire we checked the flue," he said.

The cause of the fire is unknown.

"Sometimes smoke just blows out, but we are checking into that even as we speak," Magid said.

Instead of leaving through the chimney, smoke escaped from the fireplace and set off the fire alarm at approximately 10:15 p.m.

Though the situation did not seem serious, all residents evacuated the building immediately.

Some students left the building laughing and talking because they saw no danger. One of the firefighters at the scene rebuked Caroline E. Perkins '01 and her roommates for their behavior. "It's not funny," he said.

"You have to evacuate every time the alarm goes off," said a spokesperson from the Cambridge Fire Department. "It's not a joke."

The evacuation lasted for about an hour while the smoke cleared and the alarm was turned off.

Though students took the incident lightly, in the future, they said, they will check the flue carefully.

"Oh yeah, definitely, no question about it," Atre said.