A health alert has been issued by Public Health England after police in London seized a stash of fake painkillers containing the lethal drug fentanyl.

Police found a large number of branded Percocet pills at a property in Hounslow, west London on the 27th of November. Tests found they contained the highly potent synthetic opioid fentanyl.

Regular Percocet pills contain oxycodone, a far less potent opioid, as well as paracetamol. PHE said Percocet is only used in intravenous or intramuscular formulations in the NHS.

According to reports in America, fake Percocet pills containing fentanyl have been circulating for some time. In August, singer Demi Lovato was said to have overdosed on a fake Percocet.

The UK alert follows an outbreak of fentanyl-related deaths in England around Easter last year. Some of these deaths were later linked to a gang of three men who sold fentanyl which they packed and posted from their lock-up in Leeds and sold via a page on the dark web, before being busted in April.

Deaths related to fentanyl and its analogues, including carfentanyl, jumped from 59 to 106 between 2016 and 2017 in England and Wales.

Research published this week by social care charity CGL found that 3 percent of people receiving drug treatment tested positive for fentanyl. The England-wide study among 460 people found most of them were unaware they had ingested fentanyl.