Three crew members of a Greek-flagged cargo ship docked in this Gulf coast port were killed Thursday in a work accident, Mexican authorities said.

The men died of asphyxiation when the door to a cargo hold accidentally closed, trapping them inside, according to preliminary accounts.

The crewmen - two Salvadorans and a Nicaraguan - were loading maize into the hold at the time of the accident.

Because the accident occurred in an international port, Mexican federal authorities assumed jurisdiction over the investigation.