Emergency services remain at the scene at Treforest Industrial Estate, Rhondda Cynon Taf.

Reports of an explosion shortly after 7pm on Wednesday night prompted an extensive multi-agency response.

South Wales Police declared a major incident and Cwm Taf Morgannwg health board was put on high alert for several hours.

The force has since said there were no reports of any serious injuries.

The Welsh Ambulance Service confirmed it had treated three patients at the scene before they were discharged.

As of Thursday afternoon, the fire is "largely extinguished, with small pockets of fire remaining".

More roads have reopened throughout the day and the Health and Safety Executive have joined the police and fire service to determine the cause of the fire.

Rhys Mordaunt owns RM Sports Massage and Therapy and has been based at Mindset Functional Fitness gym in Rizla House for around a year and a half.

He told Sky News he understands his room is "completely gone".

"From what I've seen, the explosion happened right next to my room," he said.

"I haven't been down there, I haven't seen it, but from what I've seen I think the room's completely gone through."

Mr Mordaunt said he was at football training when he found out what had happened.

"By that point, everything was already everywhere on the news and on Facebook and all that," he said.

"I don't know what the plan is with Mindset yet. Wherever they go next or whatever they do next, hopefully I can be part of that.

"In the meantime I'll have to sort out either a location, or a unit or somewhere to go."

He said he hadn't yet tried to reach the site so as to allow emergency services to continue their response.

"One of the guys who owns the room next to me, he said that he was there and luckily he got out," Mr Mordaunt added.

"But he's told me that the rooms are all gone so I've got a good understanding of what's happened down there now."

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Andrew Cox, who runs Andrew Cox Barbering, wrote on Facebook that the building underneath Mindset gym, where his business is based, exploded.

"The gym is heartbreakingly no longer accessible together with all the businesses inside including Andrew Cox Barbering," he said.

"Nobody is allowed near the vicinity so I am completely clueless as to what is still standing, if anything.

"I am frantically trying to work out what the next steps are regarding all appointments."