Northumbria Police has confirmed its officers believe the blaze, which started in the shed at the rear of a home in Fellside, near Quarry Lane, and left the house next to it damaged, as suspicious.
A force spokesperson said: “At 11.39pm on Friday, police were alerted by the fire service to a fire at a property on Fellside, South Shields.
“A fire believed to have originally started in a shed had then spread to an adjoining house.
"Thankfully, nobody was injured.
“At this stage, police are treating the fire as suspected arson and enquiries are ongoing. Anyone with information is asked to contact 101 quoting reference 1389 220319 or Crimestoppers anonymously on 0800 555 111.”
Tyne and Wear Fire and Rescue Service has confirmed it was called to the scene at 10.42pm and sent two appliances to put out the fire.