UPDATE: National Zoo Given All Clear, Will Open Friday

Updated at 6:30 p.m.

WASHINGTON, D.C. — A mishap when an employee at the National Zoo in Washington mixed some chemicals caused a "boom" and closed some exhibits along the American Trail area Thursday, officials said.

But, authorities have given the all clear for staff to check outdoor animal habitats on American Trail and the area will open as normal on Friday.

Zoo official said all the animals are accounted for and doing well.

“No one is hurt. No animals are hurt,” zoo spokeswoman Devin Murphy told The Washington Post. “The area has been cleared and we’re investigating what happened.”

The outdoor exhibit normally lets visitors walk a trail to view wolves, otters, beavers and other animals. Murphy said the incident happened near an otter exhibit.

The Washington DC Fire Department responded and said there was no fire. A spokesman told the Post that an employee was mixing chemicals, which likely caused an audible boom.

Fire officials are not describing the incident as an explosion.

»National Zoo photo from Google Maps