Two children and two adults were taken to hospital after a chlorine leak at a sports centre.
All users were evacuated from Strood Sports Centre last night at around 3.30pm after reports of high levels of chlorine in the swimming pool.
An eyewitness said there were eight emergency vehicles at the scene including fire engines, ambulances and an incident response team.
Four patients were taken to Medway Maritime Hospital by ambulance last night.
South East Ambulance spokesman Rich Airey said: "It was a precautionary measure and none of the patients were in a serious condition.
"People were complaining of being short of breath."
Fire crews isolated what they believed was the source of the leak and the sports centre re-opened just before 6pm.
The teaching swimming pool stayed closed for further testing.
Heru Asesimba was in the sauna when the centre was evacuated.
He said: "There was a suspected gas leak that was later confirmed as a Chlorine overload of the pool.
"Myself and other centre users were evacuated into the car park for our safety.
There were at least 8 emergency vehicles outside and a few children were taken to hospital.
"I'm ok, however, I'll be visiting a GP or hospital today to ensure my breathing has not been affected."
Carrie McKenzie, assistant director of transformation at Medway Council, said: “The centre was temporarily closed earlier this afternoon as a precautionary measure following reports of a strong smell of chlorine.
"KFRS attended and assessed and confirmed the site was safe to reopen."