Five men were hospitalised after taking what is suspected to have been a bad batch of heroin.

Emergency services were called to a Welwyn Garden City address on the night of Thursday August 19.

Herts police were alerted by the ambulance service around 10pm after a man collapsed inside what is believed to be the YMCA hostel in Peartree Lane.

While the man received treatment a further three men became unwell with similar symptoms.

All four were taken to hospital by ambulance.

Just after midnight a fifth man collapsed at an address in Knella Road and was also hospitalised.

Inspector Spencer Neil 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.

“As always, if you have any information about suspected drug dealers in your neighbourhood please contact police online at herts.police.uk/report, talk to one of our Force Communication Room operators via web chat at herts.police.uk/contact, or call our non-emergency number 101.

“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.”

A spokesperson for the YMCA said: "Our staff assisted the police in their investigation and our residents have been made aware that there is additional support and advice available if required.

"We also shared with our residents, at all our accommodation services, an alert from Public Health England that there had been an unprecedented amount of overdoses (including some deaths) which PHE believe to be linked to a highly potent and dangerous form of synthetic opiate which has particularly affected heroin users."

* A 33-year-old woman from Welwyn Garden City has been arrested on suspicion of possession with intent to supply and remains in custody.