It's believed the fire started at around half four yesterday afternoon on Dr Cullen Road – but shortly after 10 o'clock last night it had been contained to a single section.
The fire is now under control and the roads surrounding the scene of a fire at a disused factory in Carlow town have now re-opened.
Residents in the area were warned to stay indoors because it was feared the building contained asbestos, which is highly toxic.
Crews from Bagenalstown and Carlow fire service brought the fire under control at around 11pm last night.
Specialists from the Environmental Protection Agency will carry out an investigation at the scene today.
The cause of the fire is not yet know.
No injuries have been reported.