MILAN (AP) — Italian authorities have arrested five alleged human traffickers accused of murder in the deaths of dozens migrants who were either stabbed to death or perished of engine fume inhalation inside the overcrowded hold of a smuggling boat.

Italian police said the five people arrested in Sicily on Tuesday are accused of stabbing and throwing overboard some 60 men and women after passengers tried to escape the cargo hold, where many had been imprisoned.

No bodies have been found, but Italian authorities say survivors have reported seeing “friends and relatives, stabbed and stunned” floating in the sea, but were under threat and unable to help.

More than 550 were rescued Saturday while the bodies of 30, many of whom asphyxiated inside the hold, were recovered.

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