Updated 9:10pm: Two toddlers have been the centre of a major rescue response operation in waters off Auckland tonight.

The two fell from a wharf on Rangiahua Island, off Great Barrier Island.

An 18-month-old boy and a three-year-old girl are being stabilised on the island before being flown to Starship Hospital in Auckland.

The boy is in a critical condition.

The girl was found in a critical condition but that is now described as moderate.

Police, St John paramedics, and a Westpac Rescue helicopter responded to the call about 7.45 this evening.

A handful of families live on Rangiahua Island.

Emergency services received the call about 7.45.