Pictures show the extent of the operation in Blandford Street as the fire broke out.
Fire crews have been working since 6pm on Wednesday to bring the blaze under control, with much of Blandford Street expected to stay closed throughout today as investigations continue. Here we look at how the incident unfolded and the full extent of the damage.
Firefighters were called to the scene at around 6pm on Wednesday.
The street was closed off to the public.
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At the fire's peak there were five engines and two aerial ladders in use.
Firefighters were damping down the rear of the building on Thursday morning.
Emergency services at the scene.
Nobody is believed to have been hurt in the fire.
Smoke was seen billowing across the city.
Bystanders watch the blaze unfold.
Chris Lowther, Chief Fire Officer and Chief Executive for Tyne and Wear Fire and Rescue Service, gave an update on social media on Wednesday night.
"It started out just as smoke and the flames came through the roof."
Chris Lowther said: "Even at this early stage I can thank the crews for their bravery, effort and professionalism. We are here to look after our community."
Chris also said: "Our firefighters have done well to contain this job. Its not over yet though. Water supplies remain an issue and we are working hard to prevent lateral fire spread."
Bystanders told the Echo that the front of the shop collapsed with the flames.
Echo readers across the city have shared their messages of support for the region's firefighters.
Michelle Scott said: I live nearby and I heard a huge bang, it sounded like the roof had come in. You dont expect this to happen. My daughter could have been walking by just as it happened.
One witness, who asked not to be named, told the Echo: "I went out and it was just smoke at first and soon the flames were so high."
Dozens of firefighters, police officers and paramedics were at the scene.
An orange glow filled the sky in Sunderland as firefighters worked to extinguish the growing flames.
The smoke was seen all over town.
Julie Elliott MP was one of those offering support to the firefighters.
Staff from the Greggs in Blandford Street have been handing out free hot drinks and food to firefighters who worked through the night to prevent the blaze spreading to neighbouring properties.
We will bring you the latest news from the fire as we get it.