Firefighters spent two hours fighting a house blaze in Baxenden yesterday.
Flames ripped through the lounge of the house on Manchester Road at around 3.38am on Sunday, February 10.
The occupants were asleep but escaped unharmed after the smoke alarm went off.
Watch manager Steve Barnes, of Hyndburn Fire Station, described it as a serious fire.
He added: "Upon arrival crews were faced with a serious fire involving the rear lounge.
"Two fire appliances attended the incident. Four firefighters wearing breathing apparatus, hose reel jets and one positive pressure ventilation unit were used to extinguish the fire.
"The cause of the fire is been confirmed as accidental. The alarm was raised by two working smoke detectors that had been previously fitted by the fire service, which in turn allowed the occupants to escape unharmed. Without detectors this would have been a very different story due to the occupants being in bed asleep when the fire started."
For a free home fire safety check call 0800 1691125.