The death toll following a fire aboard the Norman Atlantic ferry traveling from Greece to Italy has increased to 10. Fire broke out on the Italian-flagged vessel Sunday as it traveled from the Greek port of Patras to the Italian port of Ancona. Though 427 people -- which included passengers and crew members -- were rescued, authorities continued to search the Adriatic Sea for more victims since the exact number of people aboard remains murky.

There were supposedly 422 passengers and 56 crew members on the vessel, but 80 of the people rescued were not listed on the ship’s manifest, Italian navy Adm. Giovanni Pettorino told the Associated Press. “We cannot say how many people may be missing," Italy's transport minister, Maurizio Lupi, told the AP.

The ferry was emptied by Monday and the Italian coast guard was set to inspect it and figure out how and where to transport it, CNN reported. Since it is in Albanian waters, Italian officials have to wait for Albanian authorities to give permission before they can start an official investigation, CNN said.  It’s still unknown how the fire started, but prosecutors from Bari, Italy, announced they are opening an investigation.

The vessel might have been transporting a number of travelers who hoped to get into Italy illegally, officials including Italian Prime Minister Matteo Renzi reportedly suggested. Since there may be a number of passengers unaccounted for, two Italian ships remain in the Adriatic, Fox News wrote.

Out of the 10 people who lost their lives in the disaster, one died during the rescue effort. Seven bodies were reportedly found Monday, but reports varied about whether the unidentified people were found in the sea or on the ferry. Injured travelers were treated at hospitals in Southern Italy, Fox News reported. Some suffered from hypothermia and smoke inhalation, CNN added.

Pictures taken by a passenger’s cell phone showed flames engulfing the ferry, CNN wrote. Aerial images showed a black trail of smoke emanating from the burning ship.

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