The International Organization for Migration says an estimated 4,000 fishermen are stranded on a handful of islands in Indonesia, including men revealed in an Associated Press investigation to have been enslaved.

Steve Hamilton, the group's deputy chief of mission in Indonesia, says many of the men were abandoned by boat captains in Benjina village and surrounding islands following a government moratorium on foreign fishing that has docked vessels to crack down on illegal operators.

"It is reasonable to expect many are victims of trafficking, if not outright slavery," he says.

The group helps Indonesian authorities repatriate trafficked migrant fishermen.

The year-long AP investigation found men locked in a cage. More than 40 migrant workers from Myanmar said they had been brought from Thailand and forced to work.