Police are working alongside other organisations to find the supplier of drugs believed to have caused three deaths.
Heroin users are being urged to be mindful by that there are low grade supplies of drugs being sold in the region after three people died.
Cleveland Police has said it is suspected that they used low grade heroin.
The first man – a 35-year-old from Stockton - was admitted to the University Hospital of North Tees on Sunday, February 5, and died last Saturday.
A second man from Stockton, also 35, was admitted on Monday and a 27-year-old woman was admitted in the early hours of yesterday.
A spokesman for the force said: "They both died this morning and our thoughts are with all the families involved."
Detective Inspector Jon Tapper, of Cleveland Police, is warning drug users that they are putting their lives at a greater risk by accepting low quality heroin.
He said: ”Obviously we don’t advocate anyone should buy any type of drugs - but we are aware there are batches of particularly harmful heroin on the streets which are being peddled by dealers as a higher standard than they are and they are putting people’s lives at risk.”
Police are working with partner support agencies to advise drug users of the consequences of using these products and to identify the supplier or suppliers of these drugs.