Detectives investigating four suspected drug deaths on the same day in South Yorkshire have discovered that two others fell 'gravely ill' three days later.
Three men, aged 31, 33 and 40, along with a 47-year-old woman, all died in Barnsley on Friday, with initial thoughts that the deaths could have been linked to heroin use.
On Monday, two other suspected drug users fell 'gravely ill after taking suspected illegal substances,' according to South Yorkshire Police.
Tests are being carried out and it has been established that one of the four Barnsley deaths may be linked to a pre-existing medical condition, but detectives have described the situation as 'concerning'.
They are working with detectives in West Yorkshire following the suspected drug deaths of two men, aged 36 and 27, on Saturday.
Chief Superintendent Rob Odell said: "Officers and staff have been working incredibly hard alongside other agencies to understand the circumstances surrounding the deaths of four people in Barnsley last week.
“It has since been established that one death potentially links to a pre-existing medical condition for that individual, but nevertheless this remains a concerning series of incidents.
“Two men, aged 37 and 42-years-old, were arrested on suspicion of being concerned in the supply of drugs and were released under investigation.
“We understand that there have been further deaths in the West Yorkshire region that may also be connected to drugs use. We are in contact with officers in West Yorkshire but at this stage, we do not believe the deaths are linked. We will keep an open mind as our investigations continue.
“Detailed toxicological tests are being carried out and this can take some time to produce results, so while this happens we are following up a number of other lines of enquiry.
“In addition to the deaths reported to police, on Monday, April 17 we received two separate reports of individuals becoming gravely ill after taking suspected illegal substances. Thanks to the quick actions of paramedics, those individuals survived.
“I appreciate that these are concerning events and I’d urge anyone with concerns about this matter to either contact police or, if you have taken a substance and feel unwell, to seek medical support and advice immediately.
“Our absolute priority is to keep people safe from harm and to minimise any threat to life, which is why we will continue to investigate these incidents as thoroughly and as quickly as we can.”