An oil tanker and cargo ship are both on fire after colliding in the North Sea off the coast of Lincolnshire, the RNLI said.
The lifeboat service added that it had sent four crews to the scene after the crash was reported just before 9.50am.
There have been reports a number of people abandoned the vessels following the collision around 13 miles from the coast, the RNLI added.
32 casualties were brought ashore, Martyn Boyers, chief executive of the Port of Grimsby East, said. Their conditions are unknown.
He added that there were reports of a “massive fireball”.
“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,” he said.
HM Coastguard said earlier it is currently co-ordinating the emergency response.
A coastguard helicopter took off from Humberside and headed to the scene alongside lifeboats from Skegness, Bridlington, Maplethorpe and Cleethorpes.
HM Coastguard fixed wing aircraft and nearby vessels with fire-fighting capability are also involved in the response.
The oil tanker is named Stena Immaculate and is sailing under a US flag, while the cargo ship is named Solong and is Portuguese-flagged, according to Marinetraffic.com.
The website also described the US-flagged vessel as being an “oil/chemical tanker”.
The Solong had been due to travel to Rotterdam in the Netherlands after departing from Grangemouth in Scotland this morning, according to Marinetraffic.com.
Moving images on the tracking site suggest the oil tanker had remained stationary as the Solong headed straight towards it before the collision.
It is believed the Stena Immaculate, which was travelling from Greece to the United Kingdom, was anchored at the time.
Visibility in the area had been poor before the collision, according to the Met Office.
“Areas of fog and low cloud lifting as winds increase through the morning, with some warm, if rather hazy sunny spells expected in places for a time,” it said this morning.
“Thicker cloud and a little rain moving southwards during the afternoon. Maximum temperature 14C.”