A dead bird lodged in the chimney of a gas-powered boiler was the cause of a carbon monoxide leak at a Roanoke College fraternity house over the weekend, college officials said Monday.

The fact that no one was harmed by the gas leak -- the second in two months on the Salem campus -- was attributed to a recently installed carbon monoxide alarm in the Sigma Chi house and quick action by its residents to call security after it went off.

"We're thankful that the school put them in," house resident and fraternity president Jason Nadeau said of the alarms. "Because if they were not there, we probably would have slept through the night, and who knows what would have happened."

Most of the people who had attended a party at the college-owned house Friday night had left by the time the carbon monoxide alarm went off about 1 a.m. Saturday, Nadeau said.

It wasn't clear at first to the five residents and two guests still in the house whether the alarm was from smoke or carbon monoxide detectors. But once Nadeau realized the alarm was coming from behind the locked door of the basement boiler room, he decided to call campus security at once.

Nadeau said he was influenced by a July 14 carbon monoxide leak on campus, which killed one person and sent more than 100 people to local hospitals. A malfunctioning water heater has been blamed for the leak in the Sections dormitory, which was hosting participants of two summer programs at the college.

The school had no carbon monoxide detectors at the time but has since installed them in every building on campus.

Roanoke College spokeswoman Teresa Gereaux said school officials were grateful that the alarm in the Sigma Chi house worked properly, considering that studies have found flaws in some of the commercially available brands. The school has ordered more sophisticated alarms that will automatically notify campus security when carbon monoxide is detected, but they have yet to be installed.

"I think we're just grateful that the whole system worked, which included the students and their actions," Gereaux said.

Yet once again, the school was put in the position this week of taking additional precautions against yet another possible leak. Maintenance workers were checking all of the flues and chimneys on campus, Gereaux said, and a contractor will soon be brought in to repeat the process and review campus procedures.

The boiler in question, which is used to heat water for the house's radiator heating system, was checked two months ago as part of an inspection of all gas appliances following the July gas leak, Gereaux said. It passed a state inspection conducted Nov. 1.

It appears that the bird only recently got into the chimney. Other debris, which could have come from the bird's nest, may have been washed into the flue from the outside by recent heavy rains, the school said in a news release.

"We don't believe we overlooked anything in the earlier inspections," Gereaux said.

After the flue was cleared Saturday, the boiler was tested by officials from the school and the Salem Fire-EMS Department before the students were allowed back inside, Gereaux said.

When firefighters arrived at the two-story brick house on Market Street, which sits on the western edge of campus, they found levels of carbon monoxide of about 400 parts per million. A concentration of 35 parts per million over eight hours is the maximum exposure allowed by OSHA for workplaces.

Much higher levels were found during the July 14 incident at the Sections dormitory. Hand-held carbon monoxide gauges used by firefighters showed the level to be 600 parts per million, the highest reading available on the devices.

No one in the Sigma Chi house experienced any headaches, nausea or other symptoms of carbon monoxide poisoning, Nadeau said. All of the residents have since returned. "Nobody feels that they are in any danger being in the house," he said.