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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Labour's Assembly Member Jenny Rathbone was heavily criticised for a message posted shortly after Charles Kennedy's death was announced.
An inquest into the deaths of three army reservists was told that a fourth soldier was initially pulled out of the march due to the heat.
Michael Davies, aged 71, was on holiday with his wife when he went missing late at night.