Marine traffic maps show the moment the US-flagged tanker MV Stena Immaculate collided with Portugese-flagged ship MV Solong on Monday. The collision occurred near the Humber Estuary, with several crew members still unaccounted for and dozens of casualties have been brought to shore alive. An HM Coastguard spokesperson said: "HM Coastguard is currently coordinating the emergency response to reports of a collision between a tanker and cargo vessel off the coast of East Yorkshire. The alarm was raised at 9.48am.

"A Coastguard Rescue Helicopter from Humberside was called, alongside lifeboats from Skegness, Bridlington, Maplethorpe and Cleethorpes, an HM Coastguard fixed wing aircraft, and nearby vessels with fire-fighting capability. The incident remains ongoing." Martyn Boyers, chief executive of the Port of Grimsby East, said witnesses saw "a massive fireball". He added: "It’s too far out for us to see – about 10 miles – but we have seen the vessels bringing them in.

"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."

There have so far been 32 casualties reported, but some crew members are yet to be accounted for, Mr Boyers said. Thirteen people were initially brought to shore on a Windcat 33 vessel, followed by 10 more on a harbour pilot boat, and nine on another boat.

A person called the Humber Coastguard after witnessing the crash and people fleeing the ships. He said: "Solong has collided with Tanker Stena Immaculate in the outer anchorage.

"Both vessels are abandoning. Vessels who have firefighting equipment or who can assist with search and rescue contact Humber coastguard. Vessel Stena Immaculate is carrying Jet A 1 fuel which is on fire and in the water."

A senior White House official suggested that foul play "has not been ruled out", but did not give any further details.

Transport Secretary Heidi Alexander commented: "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."