A massive explosion was heard just after 3.30am this morning at Port Talbots TATA Steelworks
Residents reported hearing three loud bangs at the steelworks in South Wales shortly after 3.30am on Friday morning.
TATA said there were no serious injuries and all fires are "under control", although two people are believed to have suffered minor injuries.
The National Air Police Service confirmed a helicopter had been scrambled to the scene.
It said: "Attended large series of explosions at @TataSteelEurope #PortTalbot.
"Tata has now confirmed there are no serious injuries and all employees have been accounted for. All fires now under control. Excellent multi agency response from @swpolice @SWFireandRescue @SWPPortTalbot."
Resident Damian Healey told Sky News he felt a "strange compression" in the air and it sounded "as though a jet were about to pass".
One man described how the blast blew his bedroom door open, while others said their entire homes shook.
Another resident said there was a "very strong smell of sulphur" and multiple helicopters hovering over the steelworks shortly after the incident.
A video shared online purported to be of the "explosion" showed several bright flashes.
Lance Davies, who lives in the area, could see the fire from his home.
He told Sky News: "It sounded like thunder at first, and that's what woke me up."
"My house shook as well, I felt a big vibration and it also woke my little boy up and my partner.
"Even people from about 20 miles away, they also heard the explosion as well."
He said the fire could have cause a bigger tragedy: "If it had happened two hours later it would have been a completely different story, because that's when the shifts change over."
South Wales Police confirmed the incident is "ongoing" and emergency services are at the scene.
It added: "Early indications are that the seat of the explosion was a train which carries molten metal into the works.
"The explosion caused some small fires which are all under control and damage to some buildings on the site."
The force have asked the public to avoid the area.
According to the fire and rescue service, there are no concerns regarding hazardous effects from the smoke.
The motorway remains open.
Aberavon MP Stephen Kinnock said the incident "raises real concerns about safety at the works" and called on Tata to "conduct a full review, to improve safety".
"It could have been a lot worse. Grateful as always to the emergency services for their rapid and effective response," he tweeted.