BRINDISI, Italy — Firefighters boarded the charred Norman Atlantic ferry in the Italian port of Brindisi on Friday to put out residual fires and allow a search for possible dead.

A blaze broke out aboard the ferry on Sunday as it was traveling from Greece to Italy, killing at least 11 people. Italy says 477 people were rescued, most by helicopters that plucked survivors off the top deck in gale-force winds and carried them to nearby boats.

The probe into the disaster widened Friday. In addition to the ship’s captain and the head of the company that built the ferry ”“ both Italians ”“ the prosecutor’s office in Bari put two other crew members and two representatives of the Greek ferry line Anek, which rented the Norman Atlantic, under investigation, the Italian news agency ANSA reported.

Towing the ferry overnight across the choppy seas of the Adriatic took 17 hours.

Several hours after the Norman Atlantic arrived in Brindisi port on Friday, a second tug was tied to the ferry to help stabilize it both front and back.

Two firefighters went aboard to check for residual fires burning since smoke was still coming out. One side of the ferry was blackened by smoke. An acrid smell was noticeable dockside. Inside the many trucks and cars on the car desk could be feeding the fire.

Once the blaze is fully extinguished and the boat stabilized in port, firefighters will start searching for bodies. A prosecutor must be on board for the start of the official inspection of the wreck to help determine the blaze’s cause.

Prosecutors fear unregistered migrants were smuggled aboard in trucks and might have died in the flames and smoke.

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