American Trail at the Smithsonian’s National Zoo. (Photo by Mark Van Bergh, Smithsonian’s National Zoo)

Update:

D.C. Fire has wrapped up at the National Zoo.

UPDATE: all readings within normal limits. units returning to service. https://t.co/PjTSPxLJBo

— DC Fire and EMS (@dcfireems) March 17, 2016

Original: D.C. Fire and EMS are responding to an incident at the National Zoo’s American Trail exhibit.

“There was a loud boom but no fire and no smoke,” says Jennifer Zoon, a communications specialist at the Zoo. “I can confirm that the incident is related to chlorine near the beaver and otter exhibits.”

“A contractor was performing routine maintenance on the life support system of American Trail. He was in the mechanical room when he smelled chlorine, which the Zoo uses for water filtration in the life support system. Upon smelling the chlorine, he exited the building and the boom occurred shortly thereafter,” Zoon says.

The American Trail is currently closed as a D.C. Fire hazmat team investigates.

NBC 4 is calling it a chemical explosion, though Zoon says that, “It is not accurate to call the incident an explosion” because there was no smoke or fire.

No one—neither animal nor human—has been injured, according to the Zoo.

@NationalZoo @WTOP Traffic Advisory/1 lane N/B & 1 lane S/B in the 3000 blk of Connecticut Ave due to DCFEMS Apparatus.

— DC Police Traffic (@DCPoliceTraffic) March 17, 2016

This post will be updated.