A major investigation is under way in the North Sea, off the coast of Hull, where an oil tanker is on fire – with dozens of casualties reported.
HM Coastguard is currently leading the response on Monday afternoon, with dramatic images being taken of the blaze from the east Yorkshire coast.
"It's too far out for us to see – about 10 miles – but we have seen the vessels bringing them in,” said Martyn Boyers, chief executive of the Port of Grimsby East.
"They must have sent a mayday out – luckily, there was a crew transfer vessel out there already. Since then, there has been a flotilla of ambulances to pick up anyone they can find."
Here is all we know so far.
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Everything we know about the oil tanker collision in the North Sea
Fire began after collision
Lifeboats and a coastguard helicopter were called at around 10am on Monday to a collision in the Humber Estuary involving the US-flagged tanker Stena Immaculate and Portuguese-registered container ship Solong.
The American tanker was at anchor, according to ship-tracking tool Vesselfinder.
Mr Boyers said there was "a massive fireball" and black smoke has been seen billowing into the air.
More than 30 casualties so far
So far, 32 casualties have been brought ashore, but some crew members are yet to be accounted for, a port boss has said.
Mr Boyers said 13 casualties were initially brought in on a Windcat 33 vessel, followed by another 10 on a harbour pilot boat, and nine on another pilot's vessel.
The more than 20-strong crew of the Stena Immaculate are all accounted for and safe after the collision, the chief executive of Stena Bulk told the BBC.
The casualties' conditions remain unclear.
One vessel was a US chemical and oil tanker
Both of the carriers involved were of huge scale.
The 183m long tanker was the US-flagged chemical and oil products carrier the Stena Immaculate, and the 140m container ship MV Solong was sailing under a Portuguese flag.
See also: What is cyanide and what are the health risks?
Large response from the RNLI
The RNLI said it dispatched four lifeboat crews to the scene of the collision and that fires had broken out on both ships.
“Four lifeboat crews have been called to an incident off the East Yorkshire coast this morning,” a spokesperson for the RNLI said.
“At 10.20am, HM Coastguard tasked Bridlington, Cleethorpes, Mablethorpe and Skegness lifeboats to support their response to two vessels that were reported to have been in collision with each other.
“There were reports that a number of people had abandoned the vessels following a collision and there were fires on both ships.”
Investigation to commence soon
Transport secretary Heidi Alexander has said that work is underway to respond to the incident, while there will be follow-ups to find out more in the days ahead.
She said: "I'm concerned to hear of the collision between two vessels in the North Sea this morning and am liaising with officials and HM Coastguard as the situation develops.
"I want to thank all emergency service workers involved for their continued efforts in responding to the incident."
A spokesperson for the Marine Accident Investigation Branch said it has deployed investigators to Grimsby.
She added: "Our team of inspectors and support staff are gathering evidence and undertaking a preliminary assessment of the accident to determine our next steps."
“Something has failed”
Captain Nigel Bassett told BBC News that there should “no doubt” about what happened once the investigation commenced, with a focus on establishing whether the incident was caused by machinery or personnel.
"Today, something has failed," he said.
As modern ships are “double skinned,” there are two layers between the hull and cargo which should be able to resist high levels of impact.
"It is designed to withstand the rupture of the cargo space," he added.
Ships continued to burn throughout the night
Nearly 24 hours after the initial collision, the oil tankers continue to burn on the North Sea.
The search was also called off for the last unaccounted for crew member after “an extensive search” from the coastguard.
“Out of the blue”
CBS News spoke to an anonymous American sailor from the Stena Immaculate, despite the crew currently not being allowed to speak to media.
Suddenly, “a massive ship came from out of the blue," he said, leaving him and the rest of the crew only seconds to react.
The Solong didn’t stop immediately but continued driving into the Stena Immaculate for what felt like 10 minutes.
Other crew members told the sailor that it didn’t look like anyone was on board the Solong.
