Council bosses have told of their concern after hundreds of tyres were dumped on rural roads in Hartlepool.
Cleansing teams from Hartlepool Borough Council picked up 300 tyres in the space of just five days.
The council estimates that the cost of collecting and disposing of them will be about £6,400.
They were found lying on the roadside or in undergrowth, which the council believes suggests they were thrown intermittently from the same vehicle.
An appeal has now been launched for information on who may have dumped the tyres, most of which were found on roads close to the A19, not far from the villages of Elwick and Dalton Piercy.
Hartlepool Borough Council's team leader for operations and grounds maintenance Garry Jones said: "Our cleansing teams just kept on bringing in the tyres and the sheer scale of the dumping has shocked us all.
"Cleaning up any fly-tipped waste diverts staff away from more beneficial tasks and also costs the council money, and when the dumping is on this scale the impact is significant.
"In this case, we estimate that the cost of collecting and disposing of the tyres will be around £6,400."
Safety is also a 'major concern' for the council, with staff forced to work by the side of roads to collect the tyres.
Mr Jones added: "Another major concern is the safety of our staff as they work on the roadside to pick up the dumped tyres and remove them for disposal.
"Dumping is also a major blight on the environment and ruins people’s enjoyment of the countryside."
The council is calling on rural residents or drivers passing through the area to report any fly-tipping or suspicious activity.
To do so, contact Hartlepool Borough Council on 01429 523333 or Cleveland Police on the non-emergency number 101.