A hairdressers was cleared of staff and customers after the smell of smoke caused concern.
Around 15 people were evacuated from Rossi, which is in Pages Building, off North Road and Cotswold Lane in Boldon Colliery, at around 10.45am today.
A crew of firefighters from South Shields Fire Station were called to investigate.
The officers found a discarded cigarette at the rear of the building had set fire to paper, with the fumes then pulled through to the shop via an air brick.
The team pulled up a couple of floorboards near the site of the fire and used thermal imaging cameras to check it had not spread and confirm the cause of the smoke.