Emergency services say an explosion at the TATA Steelworks in Port Talbot was caused by a train carrying molten metal onto the site.
A series of small fires caused by the explosion are now under control, and it is believed two people suffered minor injuries.
You can read live updates about the steelworks explosions here
Here's everything we know so far about the incident:
Residents report series of explosions
Emergency services were first contacted at 3.35am after multiple people reported a series of "massive" bangs which shook homes in Port Talbot, and could be heard from as far away as Bridgend and Tonyrefail. Some residents reported seeing a fireball at the steelworks, while others witnessed debris falling from the sky after the bangs were heard. A picture from the scene shows what appears to be a mushroom cloud rising from the scene.
Fires now extinguished, two people suffer minor injuries
It was confirmed shortly after 5.40am that the fires had been put out. A spokesman for TATA said it all its staff had been accounted for, and that there were no serious injuries. A statement from South Wales said it was believed two people had suffered minor injuries.
This video by Lance Davies shows the immediate aftermath of the explosion (Warning: contains strong language).
Origin of blast revealed
It is believed the blast originated from a train carrying molten metal onto the site, which caused a number of small fires and damaged buildings at the steelworks. TATA later confirmed that the fire had been caused by a "spillage of liquid iron as it was travelling to the steel plant".
No hazardous material released
Residents have been told they have no reason to be concerned about hazardous material released into the environment by the incident.
M4 remains open
The M4 motorway past the town remains open, meaning the incident is unlikely to cause any travel disruption.
Full investigation launched
TATA has confirmed it has launched a full investigation into what caused the explosion, while local MP Stephen Kinnock has urged the company to conduct a full review to improve safety.
