Seven people have died and two are missing after a container ship crashed into a control tower in the Italian port of Genoa, officials say.
The Jolly Nero smashed into the 50m (164ft) concrete and glass tower late on Tuesday, causing it to collapse.
Rescue workers have been searching in the rubble for survivors while divers are scouring the surrounding water.
The ship's captain is being investigated by prosecutors with a view to possible manslaughter charges.
Officials, though, have said that some sort of mechanical failure was most likely to blame for what happened.
The vessel has been impounded and its "black box" seized by investigators, according to Italy's Ansa news agency.
The accident occurred at about 23:00 on Tuesday (21:00 GMT), when a shift change was taking place in the control tower and about 13 people were thought to be inside.
Several of the bodies were recovered from an area near the tower's submerged elevator.
The Jolly Nero was manoeuvring out of the port with the help of tugboats in calm conditions, on its way to Naples, reports said.
The cause of the crash was not immediately clear, but Italian Transport Minister Maurizio Lupi said there could have been a problem with the ship's engines or with the tugboat cables.
Genoa's Il Secolo XIX newspaper quoted one of the Jolly Nero's pilots as saying: "Two engines seem to have failed and we lost control of the ship."
The head of the Genoa Port Authority, Luigi Merlo, told the newspaper: "It's very difficult to explain how this could have happened because the ship should not have been where it was."
Two tug boats were moving the vessel, there was a port pilot on board, and sea conditions were "perfect", he added.
"It's a terrible tragedy. We're in turmoil, speechless," Mr Merlo told local TV.
The ship's owner, Stefano Messina, who arrived at the port soon after the crash, had tears in his eyes as he told journalists: "We are all utterly shocked. Nothing like this has ever happened before, we are desperate."
Genoa is Italy's busiest port. Mayor Marco Doria said there was an average of 14 accidents a year, but that the incident late on Tuesday was unprecedented.
All that was left of the control tower after the crash was a buckled metal exterior staircase.
"It was an incredible sight: the control tower was leaning perilously," the port's nightwatchman told La Repubblica newspaper.
Six of those killed have so far been identified. Two of them - Maurizio Potenza and Michele Robazza - were pilots for the port. Another three - Fratantonio Daniel, David Morella and Marco De Candussio - were coastguard officers. The sixth was Sergio Basso, who worked for a tugboat operator.
Four people were being treated for injuries, two of whom were in critical condition.
"The main injuries are fractures, crushed body parts, significant traumas," emergency services doctor Andrea Furgani said.
The Jolly Nero is almost 240m (787ft) long and has a gross tonnage of nearly 40,600 tonnes. It is owned by the Italian firm Ignazio Messina & Co.
The BBC's Alan Johnston in Rome says that whatever the cause of the crash, it has revived memories of the accident involving the Costa Concordia cruise ship off the Italian island of Giglio in January 2012, which left 32 people dead.
Now another Italian-owned and -operated ship has been involved in a deadly accident and the nation's reputation for maritime safety has taken a further beating, our correspondent adds.