A man and a woman have been quizzed by police investigating the distribution of a potentially lethal batch of heroin across Teesside.

More than 20 addicts have been treated in hospitals in Middlesbrough, Stockton and Hartlepool for respiratory failure after taking wraps of the contaminated drug.

A 31-year-old man and a 40-year-old woman from Middlesbrough were arrested in connection with the supply of heroin and later released on police bail.

Cleveland Police are working to trace all addicts who have bought the contaminated heroin, which is slightly darker than normal and has a tar like appearance when dissolved in citric acid.

Detectives are "extremely concerned'' about the batch and Detective Superintendent Stewart Swinson, Middlesbrough Crime Manager said yesterday: "The use of the contaminated heroin that has gone out on the streets presents a higher risk to addicts . It's not safe to take in any quantity at all. It is imperative that addicts avoid this suspect drug.''

Anyone with information about the batch should ring Crimestoppers on 0800 555 111 or Middlesbrough Police on (01642) 303126.