American Airline jets are seen at the Miami International Airport: The man was trying to board an AA flight to Jamaica at the airport when the bag exploded

AN explosive device presumed to be destined for Jamaica, ignited yesterday while being off-loaded from an American Airlines plane, disrupting operations at the heavily trafficked Miami International Airport.

No one was reported injured in the incident, which occurred at 11:30 am but airport authorities shut down four gates, stalling operations for several hours at the usually congested Florida, United States airport.

The device called a primer which is used in firearms, belonged to a naturalised American man who was immediately taken into custody, authorities said.

Media relations manager at the Miami International Airport, Mark Henderson told the Observer that the incident was being investigated by the Federal Bureau of Investigations (FBI).

He confirmed that the airport was forced to shut down operations at four of its gates, impacting four flights. Two of the gates were later reopened.

"The gate where the plane (that) was involved in the incident came in and the one adjacent to that are still closed for now," Henderson said.

There were no major disruptions of the airport's overall operations.

Observer sources said the passenger whose country of origin was not ascertained, had hundreds of primers in his bag. He arrived at Miami from Boston, Massachusetts on an AA flight, with connection to another AA flight to Kingston.

The primer ignited as the bag was being offloaded from the Boston flight by a baggage handler who apparently suffered no injury.

And, last night American Airlines director of corporate communications for Miami, Caribbean, Latin America and US Hispanic, Martha Pantin also confirmed the incident, but declined to give details, saying only that the matter was being dealt with by the Miami Dade Police and the Transportation Security Administration.

The incident made headlines in the US yesterday, with CNN reporting that the 37-year-old passenger, whose name has not been released, had been charged with transportation of hazardous materials. If convicted, he could face a sentence of up to five years.

The 737 jet on which the passenger had travelled from Boston had 148 passengers and a crew of six.

CNN also quoted FBI special agent Michael Leverock as saying that the incident did not appear to be terrorism-related and that it was the movement of the bag across the tarmac that set off the explosion.

When the primers ignited several were said to have hit the bag handler's shoes, but there were no reports of injuries.

The bomb squad was also called in.