Drug alert: Girl (16) among five to die in Belfast
The death of a teenager is one of five since Friday being investigated by the PSNI.
Officers believe that prescription and illegal drugs, taken with alcohol, are behind at least two of the tragedies.
The 16-year-old girl died in the Great Victoria Street area of Belfast on Monday.
On the same day the deaths were reported of 26-year-old Christopher Lavery at Riverdale Park North in west Belfast; a 25-year-old man in Hannahstown, and a 28-year-old man at Utility Street in south Belfast.
There was also the sudden death of a man on Friday at Verner Street in the city centre.
Tributes were paid to Mr Lavery, who was described by one friend as a "big, gentle soul with a heart of gold".
Yesterday the PSNI and the Public Health Agency called a Press conference to update the public on their investigations into the spate of sudden deaths.
Detective Chief Superintendent Tim Mairs said enquiries were continuing.
He added that drugs were suspected in two of the deaths on Monday, and were a possibility in the other two deaths on the same day.
"While we believe there is a drugs link between two of the deaths, there is no one drug suspected to be common to all the victims," he said.
"Post-mortem examinations are due to take place to determine the causes of each of those deaths and enquiries will continue.
"Investigations are at an early stage.
"But I would like to take the opportunity to reinforce the dangers posed by taking any illegal drug or any medication which is not prescribed for you.
"Misuse of drugs can affect anyone and we recognise that many vulnerable people are being exploited for the financial gain of those higher up the supply chain."
Mr Mairs said it was a "stark reality" that more people were dying from misuse of opioid drugs in Northern Ireland than from road accidents.
Police figures show that the number of drug-related deaths here is on the rise, with 78 between January 1 and November 2 last year - a 28% increase on the previous year.
Mr Mairs added that tackling drugs remained a priority for police and pointed out that during the recent Operation Torus - which ran from February 27 to March 26 - officers seized more than £793,000 worth of drugs and conducted 389 searches resulting in 92 arrests.
Police charged or reported 74 people to the Public Prosecution Service.
Superintendent Robert Murdie said the deaths were not linked, nor had any particular trend emerged in terms of drugs.
He believes those they suspected of taking drugs consumed a variety of substances.
"It appears to be a combination of different drugs being misused, and that's from prescribed medication, illegal drugs and also alcohol," he explained.
Meanwhile, Seamus Mullen, head of health improvement at the Public Health Agency, warned about the dangers of taking drink with drugs.
"The Public Health Agency is working with the PSNI around the misuse of drugs and alcohol throughout Northern Ireland," he said.
"We would like to reiterate the message that individuals should not take drugs that are not prescribed for them by a medical professional."
The spate of recent deaths has sparked unease, particularly across Belfast where most of them occurred.
West Belfast Sinn Fein MLA Orlaithi Flynn said the community was deeply disturbed.
"The recent tragic deaths of a number of young people across Belfast has shocked the entire city," she said.
"My thoughts are with the family and friends of those who have died at this difficult time. I would call on anyone who can assist the investigation into these deaths to contact the PSNI."