A court has heard how a noxious substance released into a swimming pool happened while staff were trying to restart its pumps.

David Lloyd Leisure Ltd admitted at a hearing last month it had risked the safety of its members during the incident at its club on Ransomes EuroPark, Ipswich on February 22, 2012.

Five people required hospital treatment for breathing difficulties after the substance was released unintentionally into the pool at around 6.45am.

At a sentencing hearing which started yesterday the court was told by Pascal Bates, prosecuting, that electrical problems the night before the incident had caused pumps circulating water around the pool system to fail.

When staff tried restarting the pumps the substance, described by witnesses as brown or yellow, was emitted into the pool.

This then caused a number of customers in the pool to experience breathing difficulties with some being taken to hospital, Mr Bates said.

He also pointed out a similar situation had occurred in April 2010 when the pool alarm was sounded and the area evacuated by staff, which did not happen in 2012.

“Any reported release of noxious gases should require an emergency response,” he said.

Mitigating, Simon Antrobus said: “David Lloyd want to apologise in open court for what has happened, most importantly to its members for the symptoms they have suffered.”

He also said the company had sought independent, specialist advice following the 2010 incident and it was not the case it had not reacted to this.

He said they were not lax and complacent and had put in place a procedure which appeared to have been vindicated until the 2012 incident.

Mr Antrobus added David Lloyd had a good safety record over its 32-year history, its staff were well trained and there had been no similar incidents since.

The sentencing will conclude on a date to be decided.