Yobs have been starting nuisance fires by burning bread trays at a Wearside playing field.
A crew from Sunderland Central fire station, in Millfield, was called out at 7pm on Tuesday to King George Playing Fields, off Hylton Road.
There they found a number of the plastic containers alight.
Crew manager John Nichols told the Echo: "We're having trouble with youths doing this quite a lot.
"It looks like they're stealing the trays from supermarkets and causing a disturbance by setting them alight.
"We want to get the point across that while we have appliances dealing with these call outs, they can't be elsewhere."