Coastguards battled to pump out seawater gushing into a cargo ship holed below the water line after it collided with another vessel off Sweden's Baltic coast on Friday, a spokesman said.
The 1,430-dwt cargo ship Geta was limping towards the southern Swedish port of Karlskrona as military salvage vessel Belos used heavy-duty pumping gear in a desperate struggle to keep it afloat.
"We've put the pumps on board but we don't know if that will be enough," a coastguard spokesman said.
The spokesman denied earlier reports that a crewmember from the Bahamas-registered vessel had been injured and airlifted to hospital. He said there were still no reports of injuries.
A helicopter in the area had reported no signs of any cargo in the sea, he said, though he did not know what either boat was carrying and could not confirm a news agency report that the ship was listing heavily.
It was reported that at least one ship was carrying timber.
The larger ship, the German-registered 4,113-dwt general cargo ship Graneborg, was not damaged in the collision, which took place in sunny conditions with clear visibility.
There was no immediate explanation for the crash.
The coast guard said three of the Geta's six crew had been taken onto one of several vessels that rushed to the scene in response to its radio SOS message, and the remaining three were still on board with the engines running.