British police on Tuesday arrested on suspicion of manslaughter the captain of a ship that crashed into a tanker in the North Sea, sparking a massive blaze and leaving one crew member missing, presumed dead.

Investigations have already started into what led the cargo ship to strike the tanker carrying jet fuel on Monday, as fears remained of possible harm to the area's marine and wildlife.

The UK Coastguard, which led the operation, rescued 36 people on Monday, including all of the 23 crew on the US-flagged Stena Immaculate tanker, which had been chartered by the US military.

But a missing member of the Solong cargo vessel crew was "likely deceased", UK under-secretary for transport Mike Kane told parliament.

Humberside Police in northern England said they had arrested a 59-year-old man on suspicion of gross negligence manslaughter in connection with the collision.

Ernst Russ, owner of the cargo ship, then issued a statement saying that it "can confirm that the master of the... Solong has been detained by Humberside police in the UK".

"The master and our entire team are actively assisting with the investigations," it added.

Kane said the fire on the Stena Immaculate "appears to be extinguished" but this was not immediately confirmed by the Coastguard.

"The Solong is still alight and the fire on board the Stena Immaculate has greatly diminished," the UK Coastguard said.

The Coastguard was closely monitoring the Solong, which had broken free of the tanker overnight and was limping southwards, accompanied by four tugboats, including one which had a line attached to the stricken vessel.

AFP photos taken during a helicopter fly-over showed smoke still pouring from the Solong, while a large hole could be seen in the side of the Stena Immaculate.

The accident occurred at around 9:48 am local time on Monday when the Portuguese-flagged cargo ship ploughed into the tanker, anchored off the port of Hull.

The German owners of the Solong on Tuesday said that the container ship was not carrying sodium cyanide, as had been reported the previous day. (AFP)