EAGLE-eyed firefighters spotted a caravan on fire as they were tackling another blaze.
Fire officers based at Whitefield Fire Station were called to a house in Knowles Street, Radcliffe, at 11.30pm yesterday and they discovered two wheelie bins had been left by a door of an empty house and set alight.
It took the crew 20 minutes to put out the fire, which destroyed the bins and caused minor damage to the door.
While they were there, they noticed a faint glow coming from nearby and it turned out to be a burning caravan.
The fire spread to a second caravan and both vehicles were destroyed.
Police are treating both incidents as arson and are analysing CCTV footage from a fire engine.
A Fire Service spokesman said: “It is possible that the caravans were set on fire while we were at the other fire. It is particularly unusual for this to happen.
“We spent about two hours at the scene and managed to stop the caravan fire spreading to a steel and timber container.”
Call police on 101 with information.