Police in Dorset have issued a warning to heroin users after six people were taken to hospital having suffered adverse reactions to the drug.
Paramedics were called to eight locations in Bournemouth, Dorchester and Wareham on Saturday night.
In total, four men and two woman were taken to hospital.
Two men have since been discharged and conditions of the four remaining in hospital are not thought to be life-threatening.
Another man received treatment from an ambulance crew but was not admitted to hospital, while a further man refused treatment when paramedics attended.
Det Insp Steve Thorpe said: "Although toxicology tests have yet to confirm this, we believe that these people may have been hospitalised as a result of taking the same batch of heroin.
"They have clearly had an adverse reaction to the drug which could be as a result of this batch of heroin being particularly strong or being mixed with other substances.
"While I would never condone heroin use, it is important that users are aware that so many people have suffered such bad reactions to taking the drug last night.
"In light of these recent incidents, I'd advise family, friends and acquaintances of anyone who uses heroin to make contact with them to check on their welfare."
Five people have been arrested on suspicion of drugs offences.