The fire was reported at around 3pm on Monday 17 June 2019 at the former Trelleborg building on Halfpenny Lane.
Officers are treating the fire as suspicious and are carrying out extensive enquiries in the area.
As part of their investigation they are appealing to anyone who was in the area on Monday afternoon and saw any suspicious people or groups of people in the vicinity of Halfpenny Lane to contact them.
They are also appealing to anyone who was driving in the area between 2pm and 3.30pm and has dash-cam footage. Even if you are unaware of any suspicious activity, you may have footage that could be of use to the investigation.
If you prefer to remain anonymous, you can pass information to Crimestoppers on 0800 555 111.
Please quote reference number 12190109099.