Firemen were called to two fires involving bales of hay in Holbeach Fen and Aslackby Fen over the weekend.
Four tonnes of baled hire were alight on Ravens Drove, Holbeach Fen, at about 7.45am on Saturday which was put out with a water hose reel.
The second fire involved 30 one tonne bales on fire at Aslackby Fen, near Pointon, just before 5pm on Saturday, dealt with fire crews from Bourne and Billingborough.
Both incidents follow a spate of haystack fires in Donington, Bicker Fen and Freiston last week.
SUNDAY 2.30PM: A spate of haystack fires in Donington and Bicker Fen have raised the concerns of police this week.
About 400 tonnes of straw was set alight at a farm on Vicarage Drove, Bicker Fen, just after midnight on Friday.
Earlier the same day, straw bales were set on fire at a farm in Donington just after 8am and police are also looking into two haystack fires at a farm in Freiston which was reported just before 7.50pm on Thursday.
The incidents are being looked into by an arson task force and anyone with information should call 101.
Meanwhile, firemen from Long Sutton put out a small grass blaze on Marsh Road, Gedney Drove End, just before 10.45pm on Tuesday.