A man has been injured following a suspected gas explosion in the Bonds Street area of Londonderry.
It happened at around 10:30pm on Monday.
The man was transferred from Altnagelvin Hospital to the Royal Victoria Hospital in Belfast to be treated for serious burns injuries.
He is said to be in a stable condition.
Deputy mayor of the city Gary Middleton, who is at the scene, wrote on Twitter: "Fire service working hard to extinguish flames. Residents who have been evacuated from Bond Street are currently staying with family and friends."
A police spokesman said the area was expected to remain cordoned off overnight.