A carbon monoxide leak caused the evacuation of 150 hi-rise apartments in Montgomery County, Maryland, Monday afternoon, according to Montgomery County Fire and Rescue Service.

The Park Montgomery apartments on Piney Branch Road in Silver Spring was evacuated around 4 p.m., after C-O was detected throughout the building, likely a result of a welding project in the boiler room that wasn’t given proper ventilation.

Between 800-900 people were out on the street for several hours and evaluated by medics.

No injuries were reported.

Below is a map of where the apartment complex is located.

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