An MIT sophomore was critically injured in an unexplained fire in her dorm room Monday night.

The student, who was taken to Massachusetts General Hospital, suffered third-degree burns on 55 percent of her body, said Cambridge Fire Department Captain Kenneth Jenness.

An investigation into the cause of the fire is ongoing, Jenness said.

"When the smoke detectors went off in her single room, a neighboring student called campus police and pulled the fire alarm," said MIT Dean of Students and Undergraduate Education Rosalind H. Williams in a news release issued yesterday.

MIT police responded to the fire alarm and arrived at the student's dorm, Random Hall, at 9:15 p.m. Seven MIT police officers were treated for inhaling smoke while rescuing the student and attempting to extinguish the fire, according to the release.

The one-alarm fire was successfully confined to the student's fourth floor single.

The 92 other students living in Random Hall evacuated the building immediately and were able to return after several hours.

The dozen students who live on the fourth floor were allowed to return to their rooms by 2 a.m., only five hours after the fire began, house officials said in yesterday's release.

And from Random Hall's gray exterior, there is no longer any evidence of Monday night's tragedy.

Students in the dormitory said they have collectively decided not to speak to the press.

"We are grateful to the MIT Campus Police, the Cambridge Fire Department, the MIT Safety Office, the house masters and others for their response to this emergency," Williams said.

While speculation circulates among MIT students, there is no definite timeframe for the investigation into the cause of the fire, Jenness said.

"Sometimes investigations take long periods of time," Jenness said. "There is often legal wrangling and sometimes people don't want to cooperate."

Jenness says that as the investigation begins, fire officials will interview MIT students to develop an accurate picture of Monday night's events.