"The department also mentioned that "at this time we believe there are just two casualties with minor injuries".
"We are investigating the cause of the incident and are working closely with relevant agencies including the Health and Safety Executive". All fires have now been extinguished.
"We can confirm there are no serious injuries and all employees have been accounted for", it said.
The Port Talbot site, which dates back to the early 1900s, was acquired by Tata Steel as part of its acquisition of Corus in 2007.
Steel products from Port Talbot are sent to Tata steelworks in Shotton for finishing and coating works.
Aberavon MP Stephen Kinnock said the incident "raises real concerns about safety at the works".
He said: "It could have been a lot worse". Grateful as always to the emergency services for their rapid and effective response.
One resident tweeted: "Sitting in my bed around 3.30am heard three loud bangs. Hope everyone's okay in there".
Meanwhile, South Wales Police department said they are aware of an incident in TATA Steelworks plant.
Residents living near the plant say they heard a number of large blasts and felt their homes shake as a result.
And a fourth wrote: "I swear something just blew up in port Talbot".
"Plagued now with worry about the works. Surreal, this. Hope everyone is okay". "The explosion caused some small fires which are all under control and damage to some buildings on the site", the spokesman said.
Early indications suggested the explosion came from a train used to carry molten metal, police was quoted as saying by the report. The fire and rescue team are still conducting rescue operations at the site.