Officials say it happened in the 3300 block of Rose Trace Drive.
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When deputies arrived, EMS and the child's family were performing CPR on the toddler who was pulled from the family's backyard swimming pool.
The 3-year-old was taken to Texas Children's Hospital in The Woodlands for further evaluation.
It is unclear when or how long the child was in the pool, or if there was any supervision.
An investigation into what happened is ongoing.