The fire appears to have started in a vape shop at 105 Union Street.
The tenants of the shop were being pursued by a debt recovery service for unpaid business rates, BBC Scotland News understands.
At the time of the fire, Junaid Retail Limited had been the registered tenant since August 2024, and had not paid non domestic rates at any point during this period.
Also known as business rates, this is a tax on non-residential properties like shops and factories which helps fund council services.
It is understood that Junaid Retail Limited were being pursued for these arrears by a debt recovery service, partnered with Glasgow City Council.
The registered address for the business during this period was in Hamilton, but in recent days this has changed to an address in Glasgow.
It is understood that the landlord of the property, Afton Estates Limited, had confirmed Junaid Retail Limited was still the occupier after a business rates bill for 2025/26 was returned to the council with a claim the occupiers had “gone away”.