Firefighters and investigators boarded the wrecked Norman Atlantic ferry on Friday, after it had been towed to the Italian port of Brindisi.

They retrieved the black box of the ferry, but warned that it it still not safe to enter the car deck as it was still burning, the BBC reports.

The Italian prosecutor investigating the causes of the fire, Giuseppe Volti feared that the bodies of further victims, most probably illegal migrants could be found.

The causes of the fire, which started at the car deck, are still unknown, but the black box should aid the investigators in establishing them.

Brindisi Fire Commander Michele Angiuli said that cars, trucks and other things were still slowly burning on the ferry.

The Norman Atlantic ferry was sailing from Patras in Greece to the Italian city of Ancona, when it went on fire on Sunday.

The fire killed at least 11 people and up to 19 people are still missing, the BBC reminds.

It took rescuers more than two days to evacuate 477 surviving passengers from the burning ferry, mostly by helicopter.

The captain, owner and operator of the ship, as well as three crew members are being investigated for the causes of the fire.

Surviving passengers reported that people had fought for spaces in lifeboats and helicopter basket, while crew members looked perplexed by the events.