Theresa May will visit GSK in Maidenhead for a Q&A.
A crew from Maidenhead Fire Station, two from Reading, and one from Wokingham attended the scene at 10.30am in Loddon Drive.
They were there for about two hours and there were no casualties.
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The UK has voted to leave the European Union in yesterday's referendum - and while the Royal Borough of Windsor and Maidenhead fell into the remain camp, Slough voted to support a Brexit.