Police have echoed official warnings to drug users in south London and beyond after five more men suffered suspected drug overdoses overnight.

Public Health England revealed earlier this week that investigations were ongoing into a surge suspected heroin overdoses in the past two weeks,

There have been at least 46 poisonings resulting in 16 deaths in south London, the South East, South West and East of England, PHE said.

Investigations are ongoing but the health body said most of the cases had happened in the past 10-14 days.

And police have since added their voice to the warnings after five men in Welwyn Garden City, Hertfordshire suffered suspected drug overdoses overnight.

This Is Local London: There have been at least 46 poisonings resulting in 16 deaths across the country in recent weeks - including in south LondonThere have been at least 46 poisonings resulting in 16 deaths across the country in recent weeks - including in south London

Hertfordshire Constabulary said officers were called to an address on Peartree Lane just after 10pm on Thursday following reports a man had collapsed.

While the man received treatment, police said they were alerted to a further three men becoming unwell, with all four transported to hospital by ambulance.

It is believed they suffered suspected heroin overdoses.

Police said a fifth man was taken to hospital for treatment just after midnight following another suspected drug overdose.

Inspector Spencer Neil, of Hertfordshire Constabulary, said: "Earlier this week Public Health England (PHE) issued a warning of a sharp rise in the number of overdoses linked to people using drugs in several areas across England.

"Although at this early stage there is no evidence to suggest the incidents in Welwyn Garden City are linked to other overdose cases across the country I would like to urge those who use drugs, particularly heroin, to be extra cautious about what they are using and how much.

"Hertfordshire Constabulary will be working with PHE, the National Police Chiefs' Council and the National Crime Agency who are leading the investigation into the recent rise in overdose cases across the country."

PHE said there are early signs that the overdoses might have been caused by heroin mixed with a potent and dangerous synthetic opioid, but it is carrying out more work before it can confirm any links between the cases.

The organisation said it is “urgently investigating” alongside the National Police Chiefs’ Council (NPCC) and National Crime Agency (NCA) and will work to prevent further deaths.

PHE has issued an alert to all local public health and drug services, making them aware of the problem and asking them to reach out to drug users outside of the drug treatment system.

Rosanna O’Connor, PHE’s director of drugs, alcohol, tobacco and justice, said: “We are urging drug users to be extra careful following reports of a sharp rise in the number of overdoses potentially connected to heroin, tragically with some deaths.

“We are urgently investigating with the police and local partners. We strongly advise anyone using drugs not to use alone and to test a small amount first.”

She said people need to be aware of the signs of an opioid overdose, namely shallow breathing, loss of consciousness and blue lips or fingertips, and to act fast by calling an ambulance immediately and using the opioid antidote, naloxone, if available.