Emergency services remain at the scene of a fire at a premises on Severn Road, Treforest Industrial Estate, Rhondda Cynon Taff.
This follows reports of an explosion at a property shortly after 7.00pm, Wednesday evening.
There are no reports of any serious injuries. However, one person remains unaccounted for.
Residents living nearby have been advised to close all doors and windows while this incident is continuing.
Businesses in the area are requested to implement their own business continuity plans to deal with the on-going road closures which will affect them throughout the night and into the morning.
Significant road closures remain in place and the public is requested to avoid the area.
Deputy Chief Fire Officer Dewi Rose said: “At 7.05pm this evening SWFRS responded to repeat calls about an explosion at Mindset Gym, Rizla House, Severn Road on Treforest Industrial Estate, Pontypridd.
“SWFRS currently has 16 pumping appliances, a number of special appliances and officers in attendance. The latest from the scene is that the building, a large multi-use use two storey, commercial premises, is totally alight and at risk of collapse.
“Our partners from South Wales Police, WAST, Wales & West Utilities, NRW, RCTCBC, CTMUHB and National Grid are supporting us to deal with the incident, and at the moment our focus is firmly fixed on the emergency response.”
