AURORA, Ill. (STMW) — An athletic center in west suburban Aurora remained closed Monday morning after an accidental chemical mixture near the gym’s pool created toxic fumes.

It was not immediately known whether the the Vaughan Athletic Center, a Fox Valley Park District site, would reopen before Tuesday morning.

READ MORE: Chicago Police Officer Shot, Wounded In Calumet Heights; One Suspect Also Shot

Don Davids, Aurora Fire Department batallion chief, said chemicals used in the pool were being mixed when one of the materials was inadvertently placed in the wrong tank, causing a chemical reaction that was evident in a strong odor. The building, which contained a normal volume of customers for a Monday morning, was evacuated immediately.

Crews responded about 9:15 a.m.

READ MORE: Chicago Weather: Partly Cloudy And Breezy Overnight

Two people who were near the site of the mishap were examined by fire department responders, but they did not require additional medical attention.

Center staff members were cleared to return and collect their belongings around 10:30 a.m., but were not expected to return to work for the day. Center patrons also were to be let back in to retrieve their car keys and other necessary possessions.

MORE NEWS: View Live Radar

–Aurora Beacon News, via the Sun-Times Media Wire