It's alleged that someone deliberately tried to start a fire at the entrance of a shop in town while a member of staff was inside.
The front door of Dorset Street Stores was damaged just after 6:30am on Wednesday morning when the shop opened.
Police say the damage caused was only minimal and no-one was injured.
Officers want to speak to anyone who was in the area between 6:15-7am yesterday who might have seen what happened.
Anyone with information is asked to call 01534 612612 or Crimestoppers anonymously.

'Momentous' week in Jersey's States
Plans to charge wealthiest patients for medical travel
Railway Walk reopens 'several weeks' ahead of schedule
New bar opening at former Rojo and X site to evolve Jersey's nightlife
Former Chief Minister seeks re-election
Château Vermont to become home to new music campus
St Saviour break and entry suspect pictured posing on motorbike
'Overstretched' neurology department following under-experienced managers