More than 30 people were injured, but all the tanker crew were reported rescued.

Here is what we know about the collision between the tanker Stena Immaculate and the container vessel Solong, which set off a major pollution alert on the British coast.

- Fuel tanker hit while anchored -

The Stena Immaculate, which was carrying the fuel, was at anchor about 10 miles (16 kilometres) off the eastern England port of Hull when it was "struck by the container ship Solong", according to Crowley Maritime, the US shipping firm managing the tanker. The alarm was raised at 0948 GMT.

The Lloyd's List maritime news outlet said the Solong was carrying 15 containers of sodium cyanide, but it is not known if any of the flammable compound had leaked.

A massive fire erupted and engulfed both vessels. Crowley Maritime said the tanker was carrying jet-A1 fuel and the US Defense Department has confirmed that the US military had chartered the vessel.

The tanker "crew abandoned the vessel following multiple explosions onboard" said Crowley Maritime, which is based in Jacksonville, Florida.

Around 32 people were brought ashore on three vessels, according to Grimsby port director Martyn Boyers. Stena Bulk, a Swedish company that owns the tanker, said all of the crew on the vessel were alive.

Thirteen of the Solong's 14 crew members were brought to shore and efforts to locate the missing crew member "are ongoing", said a statement from the ship's German-based owner Ernst Russ.

- Ships ablaze -

Images showed flames and a thick cloud of black smoke rising from the wreck of the two ships. The UK Coastguard was coordinating a rescue and emergency pollution operation after Crowley Maritime said the impact had "ruptured" the tanker and set off a fire.

The Royal National Lifeboat Institution (RNLI) rescue service said there were reports of "fires on both ships".

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

A plane, lifeboats from coastal stations and other nearby vessels were in the rescue operation, the coastguard said.

- Humber traffic suspended -

Associated British Ports (ABP), which operates ports in Hull and Immingham, the stricken region, said it had halted all vessel movements in the Humber estuary that flows into the North Sea.

- Relatively rare -

The North Sea has busy shipping lanes but accidents are relatively rare.

In October 2023, two cargo ships, the Verity and the Polesie, collided near Germany's Heligoland islands. Three people were killed and two others were listed as missing.

On October 6 2015, the freighter Flinterstar, carrying 125 tonnes of diesel and 427 tonnes of fuel oil, sank after colliding with the tanker Al Oraiq eight kilometres (five miles) off the Belgian coast.

A major oil spill hit the North Sea in January 1993 when the Liberian tanker Braer suffered engine damage while going from Norway to Canada. It ran aground off Scotland's Shetland Islands and released 84,500 tonnes of crude oil.

- 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 a 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" information 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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