The Cambridge Fire Department's arson unit is investigating the fire that swept through a Quincy House suite December 30, the Fire Department said earlier this week.

The cause of the fire is believed to be a cigarette left burning on a couch by William M. Greto '87-'88 of Wilmington, Del., who was staying as a guest in the sixth-floor suite.

"I smoked a cigarette and I guess that may have caused the fire," said Greto, who is currently on leave from the College.

One of the suite's residents, Michael D. Cooperson '87, was sleeping when the blaze broke out. Cooperson is not thought to be responsible for the fire in any way. He awoke at the sound of the smoke alarm and safely left the building.

Greto said he left the room after smoking the cigarette. He returned to Quincy House at approximately 9:00 a.m. and found Cooperson running out.

Greto also left the scene safely, said Quincy House Senior Tutor Michael Donnelly.

The Fire Department refused to answer questions about the investigation earlier this week and made no comment yesterday. Earlier this week, Quincy House Superintendent Ronald Levesque said the Fire Department had termed the fire "accidental."

Greto could not be reached for comment on the arson unit's investigation.

Donnelly said that as a matter of policy, he could not say whether the College is considering taking disciplinary action against Greto. He said he believed no such action is being considered in regard to Cooperson.

The occupants of the burned suite are currently being housed in one of Quincy's guest rooms and are expected to move back into their suite later this week, Levesque said.

One of Cooperson's roommates, Miles F. Ehrlich '87, said that the common room had suffered extensive damage. Ehrlich said that, in addition to the couch, all of the room's furnishings, including a double bed, a rug, a chair, and a stereo, had gone up in flames. Ehrlich also said that some of the other rooms in the suite had suffered smoke damage.