Update: 1:57 p.m.
After investigating the cause of the fire alarm, the Danbury Fire Department deemed it safe for students and teachers to renter the building. No source of the alarm was found.
Update: 1:08 p.m.
Firefighters are smelling natural gas odors in building C of the school, which holds the chemistry lab.
Danbury High School has been evacuated due to a fire alert.
The Danbury Fire Department is on scene and investigating the cafeteria area of the school.
More to come.