WASHINGTON — Montgomery County Fire and Rescue Service partially evacuated a 12-story apartment building in Silver Spring Thursday morning after crews detected high levels of carbon monoxide that had sickened some residents.

EMS crews were originally called to the Pineway Towers condos at 8830 Piney Branch Rd. about 10:30 a.m. to respond to reports of an injured man on the fifth floor.

When crews arrived, special carbon monoxide detectors alerted them to potentially unsafe levels of the gas, according to Pete Piringer, a spokesman for the fire service.

EMS traced the source of the gas to several gas-powered power washers that were being operated in the garage below the apartment building. Most residents were able to shelter in place, but parts of the building were evacuated, Piringer said.

As of Thursday afternoon, firefighters remained on the scene to ventilate the building. Several residents were evaluated for carbon monoxide exposure, and one resident was transported to the hospital, Piringer said.

The incident occurred on the same street and just a block away from the site of a three-alarm fire caused by a natural gas explosion. Seven people, including two children, were killed in the explosion and fire at the Flower Branch apartments on Aug. 10.