Chastity, 13, was last seen in Hamilton East around 5:45pm on Saturday.
He will appear in Hamilton District Court on Thursday.
Last year the COVID-19 pandemic forced the agricultural show to go completely online.
No arrests have been made at this time.
Police confirmed the 18-month-old was hospitalised.
She denied the city was "derelict", saying she visits frequently.
"The risks were well known."
The three council-owned facilities were revealed to be dumping contaminants down the drain.
The man died of his injuries on Friday.