This video - from viewer Mark Bloomfield - shows people gathering outside, as fire crews tackle the blaze on the National Library of Wales' roof.
It is thought that nobody will be allowed back inside the library until tomorrow.
Workers were all evacuated after the fire broke out.
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Mostly dry tonight with some lingering cloud around.
Bronwen Williams, 11, and her two brothers, aged 15 and 17, are all under the legal voting age in the UK.
Hundreds of people took part in a protest march in Haverfordwest today over changes to hospital services.