Firefighters were forced to cut into the walls of a Wigan home after a householder's insulation caught fire.
An investigation is being conducted after the alarm was raised in a two-storey extension at a home in Chapel Street, Pemberton, which was reported at around 6.30pm last night.
One resident there could smell smoke - but when firefighters from Wigan station arrived there were no immediate signs of a blaze.
But watch manager Gareth Gray said that after using a thermal imaging camera, it was discovered that the fire was located within the cavity wall insulation.
Mr Gray added: "The specialist unit from Leigh was drafted in and we had to cut some holes in the walls to contain the fire."
Firefighters remained at the scene until around 10pm and were due to revisit the scene today to check that the problem had not reoccurred.
"It would appear that the cavity wall insulation was not fire retardant. This was a very unusual callout though," added Mr Gray.