A fire at the site of historic nineteenth century linen mill in County Tyrone village of Sion Mills is being treated as arson.
This is the third time that the disused linen mill has been targeted by vandals throughout the summer months.
Another section of the large sprawling site had been set on fire in June of this year.
The Northern Ireland fire and Rescue Service (NIFRS) were alerted to a fire at the the front office block of the Herdman's Mill site at around 9.15pm last night.
Twenty-three firefighters from Northland, Newtonstewart and Castlederg spent four hours tackling the blaze until 1am this morning.
The roof of the block has been significantly damaged by the fire with large portions of the structure destroyed as a result.
Due to the state of the affected area's roof, the Fire Service said the use of the hydraulic Vema platform made managing the incident much easier as fire crews were unable to enter the building.
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