BOSTON -- Hundreds of university students were evacuated from their apartment complex early Thursday morning after a carbon monoxide detector alerted residents to a dangerous leak.

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Firefighters were called to the complex at 48 Brighton Ave., about 5:30 a.m. after a resident in a basement apartment called to say a carbon monoxide detection alarm had gone off.

"My roommate came in frantic and said that the fire department was here and we had to get out," resident Rachel Smith said.

Fire investigators found that an oil burner in the heating system was not ventilating properly, according to acting district Fire Chief Ed Callahan, who said the alarm saved the residents' lives.

"We evacuated the entire building. Our readings were in the several hundreds. Zero to 10 was a safe reading. I can't emphasize enough that the carbon detector that they had in their apartment saved their lives," Callahan said.

Fumes from the building's oil burner apparently backed up into the building. The air in the basement apartment had the most carbon monoxide. The four residents went to bed feeling like they had the flu. They had headaches, dizziness weakness and nausea, symptoms of carbon monoxide poisoning.

"Smoke detectors are required by law, but not carbon monoxide detectors. Fro $25 or $30, you can save a lot of lives," Callahan said.

The students were taken to St. Elizabeth's Hospital for headaches and nausea. The rest of the students were being taken to another location.