Here is what we know about Monday's incident in the North Sea involving the tanker Stena Immaculate and the container ship Solong.

- Tanker at anchor -

The Stena Immaculate, owned by Sweden's Stena Bulk, was carrying 220,000 barrels of jet fuel, said Crowley Maritime, the US shipping firm managing the tanker.

It was at anchor about 13 miles (20 kilometres) off the northeastern England port of Hull when it was "struck by the container ship Solong", it added.

The alarm was raised at 09:48 am (0948 GMT) on Monday.

A massive fire erupted after the crash and engulfed both vessels. A UK minister told parliament that the jet fuel onboard the tanker was "the source of the fire".

Despite initial reports, the Solong cargo ship was not transporting containers of toxic sodium cyanide, said its owners, German shipping company Ernst Russ.

Crowley Maritime said the tanker was carrying jet-A1 fuel. The US Defense Department has confirmed that the US military chartered the vessel.

There is no suggestion of "foul play" over the incident, Prime Minister Keir Starmer's spokesperson said.

Despite fears of an environmental disaster, transport minister Mike Kane also told parliament that "as it currently stands, no signs of pollution from vessels is observed at this time.

"But monitoring is in place and should that change, assets in place, they will be provided as needed," he added.

The UK Coastguard said 36 people had been rescued.

Thirteen of the Solong's 14 crew members were brought ashore, said owners Ernst Russ.

The search for the missing crew member was called off late on Monday, and he was "likely deceased," Kane told parliament.

All 23 crew of the Immaculate were ashore and accounted for. One sailor was treated at the scene but declined any further medical assistance, Kane added.

- Ships ablaze -

Both ships are still alight, although the fire on board the Stena Immaculate had "greatly diminished", the UK Coastguard said.

The Solong had detached from the tanker overnight and was drifting southwards and being monitored, it said. An AFP photo showed the Solong had been devasted by the blaze and was still smoking.

Kane told parliament it was "unlikely the vessel will remain afloat".

Four further ships with firefighting capacity were on their way to the site of the stricken Stena Immaculate, according to Dutch maritime servicing company Boskalis, tasked with salvaging the tanker.

The tanker would need to be "cooled down" before the fire could be put out, it said.

The government Marine Accident Investigation Branch said it had a team at the scene already "gathering evidence" and assessing "next steps".

The investigation was being led by the US and Portuguese authorities, as the ships were flagged from their countries, UK housing minister Matthew Pennycook said.

- Proper lookout? -

David McFarlane of the Maritime Risk and Safety consultancy said there were 200 to 300 ship collisions around the world each year, but most are just a "slight bump" in port.

"The collision regulations... state that all ships must maintain a proper lookout at all times. And clearly something has gone wrong here, because if a proper lookout had been maintained, this collision would have been avoided," McFarlane told AFP.

When the flames die down investigators will look for the video data recorders on the two ships -- the equivalent of a plane's "black box" data recorders.

These should have information from the ships' radar as well as voice recordings of the bridge teams. McFarlane said this would help investigators find out if there was communication between the two ships.

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