A man has died after a spate of drug overdoses in the last week in Swansea.

South Wales Police are investigating the unexplained death of a man in the Waun Wen area of the city on Saturday.

It comes after a number of people ended up in Swansea’s Morriston Hospital after taking what is believed to be a bad batch of drugs.

Swansea Bay University Health Board has issued an “urgent warning about the dangers of taking drugs” after 12 overdoses in the area since Wednesday.

The health board had said earlier in the week that fake prescription anti-anxiety pills – being sold illegally as Valium and Xanax – was thought to be behind the cause of the overdoses.

“While initially people were warned about fake anti-anxiety drugs possibly being linked to the overdoses, it is still not clear what is behind the incidents, and other drugs could be involved,” the health board has now said .

Several people had been left seriously ill in hospital in Swansea earlier in the week and the health board contacted police due to the number of overdoses in a short space of time.

South Wales Police said the man’s cause of death is “unknown” and officers were “keeping an open mind” about the circumstances surrounding it.

Swansea Bay health board public health director Keith Reid offered his “condolences to the family and friends of the person who has died”.

“It’s important that we see drug use primarily as a public health problem and recognise its very real impact on individuals and families in our communities,” he said.

“This number of overdose cases in such a short time is highly concerning and we don’t know clearly yet what drug or drugs may be behind it so we are advising people to take extreme care.”

The health board said most doctors at the 750-bed hospital at Morriston and almost all members of the intensive care and anaesthetics teams had been involved in the care of the patients.

“We have sadly heard that these drugs have led to a death, which is a tragic waste of a life full of potential,” said Morriston’s A&E consultant Adrian Stallwood.