Arsonists set fire to a caravan in Leicester Road, Market Harborough last night.
Fire crews wearing breathing apparatus used two hoses to combat the fire which caused severe damage.
The call to the fire service was made at 7.23pm yesterday.
A fire service spokesman said: "The fire was started deliberately and the caravan was 80 per cent damaged by fire."
No-one was injured.
The blaze follows a similar incident in nearby Gallow Field Road earlier this month when two unoccupied caravans were attacked.
