GARDNER (CBS) – An apartment complex in Gardner has no heat on one of the coldest days of the winter.

Around 9 a.m. Monday, the carbon monoxide detectors went off at the Gardner Commons apartments on Elm Street after a boiler malfunctioned.

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More than 30 units were evacuated and no one was seriously hurt.

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While residents sat in their cars and a bus to keep warm, firefighters went into the building to stop the leak.

“As they went deeper into the building, those levels went up to about 2,000 parts per million, which is deadly in a short period of time,” Gardner fire captain Gregory Lagoy told WBZ-TV.

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The CO was cleared, but the heat still isn’t working, so residents have been forced to find other places to stay for the time being.