Security camera footage is set to reveal the person who deliberately defecated in the Middlemarch Swimming Pool, forcing it to close.

Middlemarch Swimming Club president Stephanie Macaulay said the pool was closed for cleaning after three "faeces incidents" in a week.

The final incident was a "deliberate attack" and was disappointing, Mrs Macaulay said.

The covered indoor pool, 23m long and 10m wide, on the grounds of Middlemarch School was "well used" and about 60 families owned a key to the facility. Casual users could hire a key to access the pool for a day, she said.

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A person defecated on a concrete area on the side of the pool on January 21.

The next day, a person defecated in the pool but Mrs Macaulay believed it was accidental.

"It was only a little bit and could have come out of a nappy."

On January 28, a person defecated a "large amount" in the deep end of the pool.

"I think the third one is deliberate because of where it was and purely by the amount ... it's annoying - there is no need for it."

After such an incident, the Dunedin City Council required the pool to be closed for 36 hours for a cleaning treatment.

The pool reopened on Monday and swimming lessons had resumed.

Security cameras at the pool were recording at the time of the latest incident and the footage was to be reviewed.

The person responsible would be trespassed from the pool but no further charges would be requested from police, she said.