The fire ripped through the Church Street building on Thursday night with firefighters spending several hours bringing the blaze under control.
But a number of nearby businesses continued to be effected the following day, with some being forced to shut up shop because of road closures.
Many say it is yet another hammer blow to businesses already struggling with reduced footfall and post-Covid downturn in trade.
Michael Evans, of the nearby Smashed Burger Bar in Miller Arcade, said: "We have not opened today and it could be all weekend.
“This is a massive blow to Preston businesses.
"It's already been a tough struggle the past few months, with Preston being very quiet for trade.
“Ourselves being an independent business look forward to our weekend trade, it's our main source of income.
"Staff to pay, rent to pay, the obvious hike in utility bills, this is literally heartbreaking. To our amazing customers who chose to dine with us this weekend we will contact them."
Nearby Rise Preston cafe, also in Miller Arcade, will also remain shut over the weekend.
"Due to the city centre fire in Preston which is ongoing, we have been informed that we cannot open today,” bosses said on social media,
"We are gutted but the safety of our staff and customers come first. We will keep you updated when we hear more."
Others forced to shut up shop include Fishers, Waterstones, Haute Dolci Dessert bar and Moss Bros clothing store. It is not yet known when they will be able to reopen.
Firefighters said on Friday morning they had not yet been able to enter the building due to structural weaknesses caused by the blaze.
They said they anticipated being in attendance until at least Monday morning.
Twelve fire engines from Preston, Bamber Bridge, Fulwood, Wesham, Leyland, South Shore, Blackpool, Great Harwood, Hyndburn, Penwortham and Tarleton attended at its height.
Crews were also supported by two aerial ladders platforms from Preston and Blackpool, the air support unit and a command support unit.