The fire broke out on board a small oil tanker off Germany Friday, and seven crew were rescued from the burning vessel in the Baltic Sea, emergency services said.
Eyewitnesses reported a loud explosion around 9:15 am local time (0715 GMT), said local newspaper Ostseezeitung, and dark smoke soon billowed from the ship, which the report said is used to resupply vessels at sea with fuel.
"A fire broke out on the Annika tanker on Friday morning," the Central Command for Maritime Emergencies said, adding that the vessel was carrying about 640 tonnes of fuel oil.
"All seven crew members on board were picked up and brought to shore," they said, later adding that several of them had sustained minor injuries.
Emergency service vessels and helicopters were deployed to fight the fire on the ship, 4.5 kilometers (three miles) offshore in the Mecklenburger Bay, in waters between the towns of Kuehlungsborn and Warnemuende.
The German-flagged ship is 73 meters (240 feet) long and 12 meters wide.
Video published by Bild Daily online later showed a fire-fighting vessel aiming a powerful jet of water at the ship and no more large flames or clouds of smoke visible.
Around six hours after the blast a central command spokeswoman told AFP that there was "no oil escaping at the current time".
The central command added later that "the fire is still burning in the machine room" but that fire services had been able to board the tanker to assess the situation.
"For operational reasons, we have decided to continue fighting the fire at a mooring" after the vessel is towed to the port of Rostock, the statement said.
"The condition of the ship is being observed by navigators and is currently judged to be stable."
A maritime police spokesman in the state of Mecklenburg-Western Pomerania said that a full investigation would only be possible once the fire has been put out.