A small child is in hospital in a critical condition after a medical event in Broadlands, in the Waikato, say police.

A police spokeswoman said emergency services were first called to the private address around 5.49pm after reports a 3-year-old nearly drowned.

"The child is now in a critical condition in hospital and this is thought to be the result of a medical event, not a drowning," she said.

The child was flown to hospital, according to Stuff.