Spanish police have detained the captain and two senior officers of a cargo ship, on suspicion that they cast four Senegalese stowaways adrift.
The captain and two officers - all South Korean - were arrested when their Panamanian-registered ship, the Wisteria, docked in a Spanish port.
Crew members reportedly said officers had forced the stowaways into a tiny one-man raft and cast them adrift.
Experts say they can only have survived if they were spotted by a passing ship.
The stowaways last known position was more than 1,000km south of the Canary Islands.
Under Spanish law, the Wisteria's owners would have had to pay for the repatriation of the stowaways if it had docked with them on board.
From the newsroom of the BBC World Service