Seven people have been arrested today on suspicion of conspiracy to supply heroin.
A 35-year-old man and a 27-year-old woman were arrested in Hopper Terrace, Shotton Colliery.
A 28-year-old man and a 59-year-old woman, were arrested in Sandy Lane, Liverpool.
A 40-year-old man was arrested in Rugby Street, Hartlepool; a 37-year-old man and a 33-year-old woman were arrested in South Parade, Hartlepool.
A police spokesman said: "The suspects were arrested this morning by officers from Durham Constabulary’s specialist crime operations unit, assisted by police officers from Cleveland and Merseyside.
"They are being held for questioning at police stations in Durham and Liverpool.
"The arrests follow an inquiry which began last summer after a drug was seized when a vehicle was stopped in the Shotton Colliery area."