Fire crews from Llantwit Major, Cowbridge and Bridgend are dealing with a fire at the Vale Business Park in Llandow.
South Wales Fire and Rescue Service has confirmed that there is no asbestos within the building, but they are asking people to keep their windows and doors closed.
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Heavy, thundery showers will clear northwards through the morning, allowing it to turn mostly dry and bright for many.
Some locally heavy showers are possible overnight, particularly in the east, where some thundery downpours are possible.
Wayne Pivac praised Scarlets' attacking style as they secured the Guinness PRO12 title with a stunning 46-22 success against Munster.