The fire that damaged part of the roof at the National Library of Wales was started by accident by workers using a blow torch.
An investigation into the cause of the fire has found the device used by workers on the roof caused some wood behind external cladding to ignite.
Two workers were carrying out repairs on the roof at the time, but nobody was injured in the blaze.
Before answering today's urgent question, the Culture Minister had previously issued a written statement about the National Library fire. John Griffiths said early indications gave cause for optimism.
He said it's too early to say how much financial support the National Library will need but said the Welsh Government was working closely with Library staff.
The Culture Minister John Griffiths has told AMs that it would be 'premature' to say how much financial support the National Library of Wales will need following last week's fire. Answering an urgent question in the Senedd, he said he would be visiting the Library to see the damage for himself.
The Welsh Government will have to tell Assembly Members what support it's offering the National Library of Wales following the fire which broke out last week. The Presiding Officer has allowed an urgent question from Plaid AM Elin Jones.
The National Library of Wales will re-open to the public today after a section of the building was destroyed by fire on Friday.
A small part of the collection suffered water damage and is being examined by a specialist salvage company.
Up to 300 staff and 100 visitors were led to safety when the alarm was raised. It took 60 firefighters nearly four hours to bring it under control.
An investigation is currently underway to discover how the fire started.
The Director of Public Services for the National Library of Wales says work there is continuing as usual following Friday's fire.
The building will re-open to the public tomorrow.
Around 70 National Library of Wales staff could be relocated as investigations continue into a fire which broke out on Friday.
The building remains closed today.
David Cameron and David Jones fired several shots at the Welsh Government during the Conservative conference in Swansea.
The Prime Minster compared Carwyn Jones' administration to the "Muppet Show" in what many saw as a speech designed to galvanise the party's grassroot as the party look towards the 2015 general election.
Welsh Secretary David Jones went further, criticising Business Minister Edwina Hart's handling of Enterprise Zones as "Soviet style developments' and urging the Welsh Government to follow the UK Government's model.
He criticised planning policy and described plans to install sprinklers in new houses as "bizarre."
The Clwyd West MP said "people don't care where policy is developed...we have to cooperate if we are to succeed."
When the Tories took office "the respect agenda" was the watch phrase. No mention of that today as the party seemed to be stepping up its efforts for a Conservative Government in 2015.
Mid & West Wales Fire Service told ITV News that firefighters will remain at the National Library of Wales throughout the day, as investigations continue into the fire that damaged the building's roof on Friday.