Tilson said it was not clear whether the boy had been supervised.
Water Safety regulations stipulate that children under 8 must be supervised by a parent or caregiver aged 16 or older.
Police were at the pools this afternoon and WorkSafe New Zealand has been notified.
In January a 7-year-old boy died a day after he was revived following an incident at the nearby Palm Springs Thermal Pool in Parakai.
He had been found unresponsive at the bottom of the pool at around 11.10am on January 15. Paramedics carried out CPR on the boy, and he was rushed to Starship children's hospital in a critical condition by the Westpac Rescue Helicopter.
However, he died in hospital the late the following day.