Story highlights The conveyer belt did not start moving until after the mother placed her baby on it

The child was fatally injured by the carousel's rollers, authorities say

The mother, an American, also had another young child with her

The conveyer belt of a baggage carousel that killed a 5-month-old at an airport in Spain was not moving when his mother set him on it, a Spanish Civil Guard spokesman in Madrid said Friday.

But soon afterward it started moving, and the child was carried to the end, where his head was injured by the carousel's rollers, said the Civil Guard spokesman, who by custom is not identified.

The infant's mother, an American, arrived at the Alicante airport late Wednesday on a flight from London's Gatwick airport with her baby boy and another young child, said a spokeswoman for Spain's airport authority, AENA.

The father, who is Canadian, was already there waiting at the Alicante airport, she added.

An unidentified security guard at the airport told CNN affiliate Atlas she didn't see the incident, but was told that "the mother apparently put (the baby) down on the conveyer belt when she went to reach for something. He was crushed by the conveyer belt and it killed him."

With the baby bleeding, officials summoned airport medical personnel, who rushed to the scene but were unable to revive the infant, the Civil Guard spokesman said.

The carousel for oversized luggage is a flat, black rubber-type belt that moves in only one direction, ending with a series of horizontal rollers that slow the luggage to a stop, for pickup. It's several feet long and passengers can stand on either side of it or at the receiving end, said the airport spokeswoman, who by custom is not identified.

The Civil Guard spokesman said the baby's weight activated the motionless conveyor belt and started it moving, but the airport spokeswoman, citing a baggage worker, said Friday that the belt is not activated by weight.

A day earlier, the spokeswoman said the conveyor belt is activated only when oversized bags are sent out on it for pickup.

"I don't know what happened," the airport spokeswoman said. "The Civil Guard will determine that after the investigation."

After the baby was pronounced dead, the family had to wait for a judge to arrive, by Spanish law, so that the body could be moved. Civil Guards took statements from the parents at the airport, the airport spokeswoman said.

The Civil Guard says it is treating the incident as an accident.

The baggage belt for oversized luggage -- which includes infant car seats and baby strollers -- is at one end of a large baggage claims hall at the Alicante airport, which handles 9 million passengers a year, the spokeswoman said.

The baggage carousel is in a secure area, and passengers go through it to claim their bags before they exit into the public arrivals hall. The father of the baby would not have had access to that area, the airport spokeswoman said.

Civil Guard and National Police spokesmen in Alicante confirmed the nationalities of the mother and father as American and Canadian, respectively.

Spanish newspaper El Pais reported the family had come to the Alicante area, on Spain's Mediterranean coast, for vacation, but authorities would not immediately confirm that.