A rogue batch of heroin is thought to be responsible for the deaths of two Essex drug-users over a 24-hour period.
Essex Police officers found the body of a man in his 20s after they were called to a property in Maple Way, Colchester, on Wednesday.
Officers discovered the body of another man at a separate flat in Maple Way on Thursday as they carried out inquiries in connection with the first death.
A post mortem examination on the first body revealed nothing suspicious.
An examination of the second body will take place next week.
Unusually strong batch
Three people died from drug overdoses in Colchester in October and November, last year, so a police investigation will look at the circumstances and backgrounds of all five deaths.
Det Insp Stuart Smith said: "We are following up the possibility that a bad batch or unusually strong batch of heroin is in circulation.
"We are gathering intelligence and working closely with other agencies in the area to try to establish where the drugs came from and then take the necessary action."
He added: "In the meantime I hope these tragedies serve as a strong reminder to potential users that they are gambling with their lives if they take drugs."