"They comforted the child and administered first aid until medical staff arrived."
A full investigation of the incident was under way, he said.
A St John spokesman said they transported the toddler to Middlemore Hospital.
He was in a serious but stable condition, he said.
"We understand it was a conveyor-belt-related incident."
A Middlemore Hospital spokesperson said the boy was in a stable condition.
Staff at Auckland International Airport were reviewing the security footage to establish what had happened, and how.
Auckland Airport general manager operations Anna Cassels-Brown said its "first concern is for the welfare of the wee boy and his mum".
"We have also advised WorkSafe NZ this afternoon, and have started our investigation to find out how this happened."
Police confirmed they were aware of an incident but referred the Herald to airport management and Aviation Security.
Overseas, a number of children have passed through baggage conveyor belts in recent years.
In 2006 a woman passed her one-month-old grandson through the X-ray machine at Los Angeles International Airport.
The Guardian reported that a security worker saw the baby entering the machine sitting on a plastic bin intended for hand luggage and jackets.
That official managed to pull the bin out along the conveyor belt.
In 2013, a five-month-old boy died on a baggage carousel at a Spanish airport after his mother put his baby carrier on the conveyor belt and it became trapped in the machine.
Spanish police said the weight of the baby carrier activated the special carousel for outsized luggage, carrying the infant off to the entrance of the bag drop.
