Montgomery County Fire and Rescue Service personnel are at the Bethesda Marriott (5151 Pooks Hill Rd.) after the building was evacuated because of a fire alarm.
MCFRS officials believe the alarm is the result of a chlorine-like chemical odor that could have come from a pool cleaning crew working in the hotel this morning.
A hazmat crew is on the scene. One person, who is reportedly having trouble breathing, is being treated at the scene.
Memorial Day weekend events from around the nation, and the D.C. area, captured in photos.