Damascus, MD – Firefighters detected high carbon monoxide levels in a building in Damascus, Maryland, Thursday night and 10 people were evaluated for possible carbon monoxide poisoning.

Chopper4 footage showed firetrucks, ambulances and police cars in a shopping center.

Montgomery County firefighters and medics responded to the 9800 block of Main Street about 5:45 p.m. after receiving a report of several people sick in a building.

First responders arrived and found high levels of carbon monoxide.

A “mass casualty bus,” which can be used to take several people to a hospital at once, is at the scene.

Several businesses in the area were evacuated.

Firefighters suspected the source of the issue was a propane “floor scrubber” that was used inside earlier in the day. They think the carbon monoxide then got into a shared ventilation system.