Nine children were among the swimmers evacuated from a pool yesterday after a chemical leak.The alarm was raised by staff at Diss Swim and Fitness Centre after the youngsters began coughing and spluttering as they splashed about in the water.

Nine children were among the swimmers evacuated from a pool yesterday after a chemical leak.

The alarm was raised by staff at Diss Swim and Fitness Centre after the youngsters began coughing and spluttering as they splashed about in the water.

The emergency services were alerted at 2.50pm, with three ambulances sent to the scene in addition to two ambulance officers in a rapid response vehicle. Fire crews from Diss and Harleston, and a chemical incident unit from Sprowston also attended, along with officers from Diss police station.

About 18 people, including members of staff, were treated by paramedics for the effects of sodium hypochlorite - a liquid used to disinfect the pool which is derived from chlorine. None of the swimmers needed hospital treatment and the children returned home with their parents, who were given advice about their care.

Teresa Church, clinical field operations manager for the ambulance service, said: “The children were puffing and splashing in the pool, but nobody had to be rescued. As soon as they got outside into the fresh air the children started to feel better. I wasn't first on the scene, but I don't think we had to put anyone on oxygen.”

Fire service spokesman Andy Heginbotham, station manager at Thetford, said that following evacuation of the pool, a hazard area was set up and the building was ventilated to remove fumes.

The pool is owned by South Norfolk Council, and Chris Cook, the authority's head of leisure and cultural services, said emergency action plans had been put into effect as soon as staff became aware of the problem.

“Obviously safety is of paramount importance,” he said.

“I received a call at about 3.15pm from my colleagues at the pool. The situation at that time was that there was a company we had contracted to undertake some work at the swimming pool plant. They isolated where they were working, which is quite normal practice and safe.

“When the pumps were restarted, a slug of disinfectant went into the water. It caused some discomfort to the nine children. There was coughing and nausea, but none have been referred for hospital treatment.”

Mr Cook said they immediately launched an internal investigation, with the council's health and safety manager, and other officials sent to the scene yesterday afternoon.

He added: “We will look at every element of the situation to see if there are any lessons to be learned.”

The swim and fitness centre was given the all clear to re-open at about 5.50pm last night.