By Jan Carabeo

NORRISTOWN, Pa. (CBS) – Apartments in Norristown, Montgomery County were evacuated overnight and a busy stretch of business was shut down because of elevated carbon monoxide readings.

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Fire officials responded to reports of a fire at AutoZone on Main Street around midnight. Smoke from the underground electrical fire involving PECO equipment then backed into several businesses, causing the elevated levels.

Crews were able to put out the fire quickly and detected the dangerous CO levels afterward. Fire officials say crews then ventilated the businesses, checking levels once again and have cleared the scene.

While going door-to-door making sure nobody was inside the buildings, crews discovered an unrelated gas leak at a nearby apartment on Main Street.

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Six tenants from two units in that apartment were evacuated for a short time, but have since been allowed back inside their homes.

No injuries were reported at either location.

Crews are continuing to monitor CO levels to make sure they are safe.

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PECO will now work to find what caused the underground problem and will likely have to turn off power to do that work. This would force closings at several businesses in the area.