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.