According to the Guardian newspaper, Italian police have arrested two suspected people traffickers among the survivors of the migrant boat that capsized off the coast of Libya on Sunday, as the United Nations said it believed that at least 800 people died in the sinking – the worst such incident ever in the Mediterranean.

Prosecutors said they had detained 27-year-old Tunisian Mohammed Ali Malek, believed to be the captain of the vessel, and Syrian national Mahmud Bikhit, 25. The two were taken from a group of 27 haggard survivors who arrived in the Sicilian port of Catania on Monday evening. The two were charged with people trafficking and the captain was also charged with reckless multiple homicide in relation to the sinking.

Survivors had earlier told investigators that they believed the vessel capsized after a collision with the King Jacob. Some told the Ansa news agency that the captain of the migrant boat was carelessly steering the vessel – and therefore could have rammed into the cargo ship – in order to avoid being identified later as the captain.

The King Jacob has been involved in four other rescue operations, according to Italian press reports. Commercial ships have played an important role in rescue operations, responding both to the calls of migrant ships that are in distress and requests for help from the Italian coastguard and navy. Aid agencies say such commercial vessels have become invaluable partners to Italian officials in cases when they are closer to distressed boats than the Italian rescue boats are. According to the IOM, commercial ships helped rescue 40,000 people last year, even though aid agencies and others have said the vessels are not really equipped to handle such sensitive rescues.