Central Otago District Council (CODC) are reviewing pool procedures after two children were locked in the Alexandra Pool after hours during the weekend.
The children, aged 13 and 10, were left in the changing room on Saturday night after staff had exited the building and closed the facility for the evening.
CODC group manager - community experience David Scoones said staff had a "well-established" practice of checking the changing rooms before leaving.
However, the staff members, who were "well-experienced and had closed the facility many times before", failed to do a final check.
By the time staff were alerted to the situation, the children had left the building through a self-releasing door.
Staff later checked the building to make sure all was in order.
Mr Scoones said the council was taking the matter very seriously.
"We sincerely apologise to the children, the parents and the community for this lapse.
"It should never have happened, and we will be taking steps to help ensure this doesn’t happen again."
CODC were undertaking a full review and would be holding a mandatory staff meeting to discuss the importance of closing procedures.
Safety was paramount in the pool environment, Mr Scoones said.
ruby.shaw@odt.co.nz, Cadet reporter