A spokeswoman for the Alicante airport management company Aena said the baby and his American mother arrived at the airport late Wednesday on a flight from London.
The baby's father, a Canadian, was waiting for them at the airport's arrivals zone when the incident happened.
A Guardia Civil spokesman told British newspaper The Independent that the investigation is still in the early stages and they are looking at CCTV footage, but it seems that it was an accident.
"The mother left the baby on the conveyor belt, which can be activated by detecting weight or by an airport employee," the spokesman said.
"It seems that the baby carrier's weight activated the belt and the child was trapped in the rollers in the drop zone."
Despite attempts to resuscitate the baby, he was pronounced dead at the scene.
Media reports said the family were in Spain for a holiday in the nearby resort town of Denia on eastern Spain's Costa Blanca.
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