A house fire which ruptured a gas main in Blackburn, forcing the evacuation of nearby homes, may have been started by a candle, the fire service said.
About 30 homes were evacuated because of the danger of an explosion from the house In Wellingon Road on Monday
Firefighters returned to the house on Tuesday morning to carry out an investigation into the cause.
Watch manager Phil Jones said initial inquiries suggested an unattended candle was to blame.
Fire crews were called to reports of the fire at about 1900 BST by a neighbour who heard a smoke alarm sounding inside the property.
They were met with a "very intense fire" which appeared to be quickly spreading, said Mr Jones, of Lancashire Fire and Rescue Service.
Jet of flame
"The main problem for the fire service at this incident was that there was a ruptured gas main due to the intensity, which led to an evacuation of approximately 50 people from the surrounding area," he added.
"Due to the ferocity of the fire it had burnt through, causing a large gas jet to go up into the first floor… it's quite a while since I've seen one with such intensity and heat."
About 50 residents were moved from their homes for a short period while engineers isolated the gas supply.
Mr Jones said the cause of the fire was being treated as accidental, possibly as a result of an unattended candle.
"We can't say enough how important it is if you do have candles have them in the right holder and to not leave them unattended as things like this happen," he added.