Gardaí have boarded a 40 metre, Mongolian-registered cargo ship anchored in Dublin Bay, just over a mile off Dun Laoghaire.
Officers from the Immigration and Drugs Bureau, along with customs and the naval service, will search the ship this evening.
It was ordered to leave French territorial waters and is being investigated here on suspicion of people trafficking.
Detectives will check passports, search the ship and examine the conditions of those onboard. They also have the power to refuse those on board permission to land in Ireland.
