Police are again appealing for information about a fire at the old Groves Road store last week.
The building, which is being renovated, was discovered alight by fire fighters shortly after 2.30am on Thursday.
They had responded to an automatic alarm at the nearby National Sports Centre.
By the time crews started tackling the blaze, ten foot flames had burnt through the roof, which partly collapsed.
The blaze was brought under control and extinguished by the fire fighters, who were at the scene for three hours.
There were no injuries.
A joint investigation was launched to establish the cause of the blaze.
Anyone with information is asked to ring Police Headquarters on 631212 or the anonymous Crimestoppers number, 0800 555 111.