Police are investigating whether the sudden deaths of a number of people in Belfast are linked to drug or substance abuse.
The PSNI said they included teenagers and people in their early 20s.
Ch Supt Chris Noble said although post-mortem examinations had been carried out, police were waiting for the results of toxicology tests to determine the cause of death.
Three people are believed to have died since Boxing Day.
Ch Supt Noble said: “Our advice is very simple.
“Do not take illegal drugs; do not take prescription medication that has not been prescribed for you and do not mix either with alcohol.
“The consequences of ignoring this advice can be life-threatening.”
Police said possible links to drug or substance abuse were “strong lines of enquiry” in some of the deaths.
“The consumption and mixing of illegal drugs can be a lottery of death as it is often unclear what the substance is, its strength or the harm it can do to your body,” he added.