At least twenty people were taken to hospital — six of them in serious condition — following an accidental release of chlorine gas Wednesday morning at a sports centre in Summerside, P.E.I.

Those in serious condition are suffering from respiratory problems, and two are in intensive care. Four others required increased observation in case their symptoms worsen.

The others are expected to be released before the end of the day.

A worker mixing chemicals in a maintenance room at Credit Union Place accidentally combined chlorine and acid, releasing the gas, and forcing the evacuation of the building at 8:30 a.m.

Fire trucks on the scene at Credit Union Place. Lindsay Carroll/CBC

People were in the pool for a morning swim at the time, and hurriedly left. Kevin (Boomer) Gallant of CBC News said people were outside in their bathing suits in the 8 C weather.

"Some people came out of the change room, they were falling up against the wall and throwing up into buckets, and we were all told to exit the building," said Gallant.

"Once you got outside the pool into the hallways, the gas … was just choking."

For a brief time, Prince County Hospital initiated a code orange to deal with the incident, calling in extra staff. Officials at Credit Union Place were calling members who might have been in the building at the time.

Many people who were evacuated from the building simply went home. Officials wanted them to go to hospital to check for related health problems.

Chlorine gas can cause acute damage to the upper and lower respiratory tract.

Fire Chief Jim Peters and Occupational Health and Safety cleared the facility to reopen to the public at 12:30 p.m.