A pipe beneath Mt. Auburn Street leaked large bubbles of natural gas and forced an hour-and-a half evacuation of Adams House last night.

Just before 9 p.m. last night, a passerby on Bow St. reported to the Cambridge Fire Department (CFD) a strong smell of gas. Firefighters arrived a few minutes later and, using gas probes, began to take readings in and around Sorrento Square.

Moments later, a firefighter found what he called an "explosive" reading of gas in the basement of Randolph House, across Plympton Street from the main Adams House foyer.

Assisted by Harvard facilities personnel, the Harvard University Police Department (HUPD) started to evacuate the whole of Adams House "as a precaution," according to Edward Mahoney, a CFD deputy chief.

Andor I. Meszaros '02, who lives in Randolph, said he could smell the gas for at least half an hour before HUPD arrived to evacuate him.

"The officer said there was a gas leak, and that we should crack our windows and get out," Meszaros said.

Officials decided not to activate the building's fire alarm because an errant spot of electricity from an alarm box could have sparked an explosion, they said.

Though most students left immediately, HUPD officials said they took extra precautions to ensure that everyone got out safely.