Police have issued a warning after 14 heroin overdoses were recorded in the last 24 hours, including one fatal incident.
Cleveland Police, with the North East Ambulance Service and Public Health England, said there was a particularly dangerous grade of the class A drug in circulation.
A 50-year-old from Stockton, Teesside, has died, police said.
This bad batch of drugs was centred around the Oxbridge area of Stockton.
There was also one victim brought to hospital from Middlesbrough.
Cleveland Police said people using streets dealers should be particularly cautious.