A blaze that broke out at the Tata Steel plant in Port Talbot is thought to have been started by a lightning strike.
The company said no one was injured in the incident at the plant's coke ovens and manufacturing would restart once safety checks had been completed.
Images on social media showed flames and smoke coming from the site.
The Mid and West Wales Fire Service said it was alerted shortly after 8am to reports of the blaze and six crews were dispatched.
Appliances from Port Talbot, Neath, Morriston and an aerial appliance from Swansea West attended the scene in south Wales.
"I can confirm that the fire has been extinguished and the power supply has been re-established at the plant," a brigade spokeswoman said.
"The crews are beginning to leave but some are staying to monitor the situation should anything escalate."
Last month, Tata announced 750 job cuts at the site, among 1,050 across the UK.
A Tata Steel spokesman said: "We can confirm that there has been a fire at our Port Talbot coke ovens this morning.
"No one was hurt. Following the necessary safety and operational checks, we will be looking to restart manufacturing operations today.
"Initial investigations suggest a lightning strike led to the fire at the site's coke ovens."
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