"Asbestos has not been confirmed at the site" said South Wales Fire & Rescue Service.
"However if asbestos is confirmed, this does not pose a safety risk to the public as heavy rainfall and water from firefighting will prevent the asbestos from spreading"
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Seven Welsh sites are in the running to be Heathrow logistics hubs which would deliver a number of skilled and semi skilled jobs in Wales.
Cloudy with outbreaks of patchy light rain at times, particularly across central and southern parts.
Wales are looking for a new manager after Chris Coleman resigned in order to take the vacant job at Sunderland.