POLICE say two people became "gravely ill" on Monday after taking drugs that are believed to be linked to the deaths of four people last week.

Police say enquiries into the circumstances surrounding the deaths - believed to have been caused by heroin overdoses - are ongoing.

Chief Superintendent Rob Odell said: “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.”

If you have any information that could help police with their investigation, call 101 or email enquiries@southyorks.pnn.police.uk quoting incident number 164 of April 14 2017.

You can also give information anonymously to Crimestoppers on 0800 555 111.