"Technically it's in the library, but it's not like it was amongst rows and rows of valuable books - it was near the library."
Ms Edmond said nobody was hurt in the fire, which was put out later this morning.
She said the area remained closed while property damage was assessed and the Fire Service investigated the cause.
Acetylene is an odourless gas used by welders, but Ms Edmond said she did not know if construction work was taking place at the time.
It was not yet known when the buildings would be reopened.
Crews from eight fire trucks attended the fire.
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