Traders were worried a fire in Hendon would spread as smoke billowed from an empty shop this afternoon.
Eli Nehman, owner of Deli Express, called the fire brigade when he saw smoke coming from the adjacent building in Brent Street shortly after 1pm.
The three story building used to contain a supermarket on the first floor, which is currently being renovated, and has two floors of flats above.
Mr Nehman, who has been in Brent Street for 21 years, said: “I could smell the smoke but I thought it might have something to do with the builders next door.
“Five minutes later somebody came in and said there was a fire. I was worried it might spread here.
“I could see the smoke coming out from a hole in the wall.”
Twenty people fled the building, but firefighters had to evacuate ten more when they arrived on the scene.
Sarah Wade who was shopping in Brent Street at the time said: “I was worried because you never know how quickly a fire can spread. I’m just glad no one was injured.”
Approximately ten firefighters helped put out the blaze at 2.07pm.