The force launched an investigation and issued a warning not to eat the chocolate, after several people reported feeling unwell.

A 63-year-old woman was arrested earlier this week "on suspicion of administering a noxious substance" and is helping police with their inquiries after being released on bail, the force said.

Officers carried out forensic testing in response to rumours the chocolate bars had been laced with drugs.

Detective Inspector Luke Todd said on Wednesday that there was, at the time, "no evidence to support claims the chocolate bars contained any illicit drugs".

However, the forensic testing has now revealed a "small number" were discovered to contain "quantities of the hallucinogenic drug psilocin and THC" - the main psychoactive chemical in cannabis.

According to the European Monitoring Centre for Drugs and Drug Addiction, psilocin is a compound found in fungi that have hallucinogenic effects when consumed.

The majority of the chocolate bars showed no traces of drugs or "anything out of the ordinary", Chief Inspector Chris Sutcliffe said.

"We are confident the affected chocolate was limited to one small batch, which we are aware of, and there is no evidence to suggest it was more widely distributed," he added.

"The chocolate bars were reportedly sold from a stand at Mansfield Market last Saturday (25 November) and were wrapped in gold packaging or sold in orange-coloured boxes marked "Cali-Gold".

The "small number" of people who ate the chocolate and felt unwell are now fully recovered.

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Anyone who bought the chocolate and still has it in their possession is being urged to contact the police to hand it in.

The force is working alongside the Food Standards Agency (FSA), the UK Health Security Agency and local authorities to investigate.

The FSA's head of incidents, Tina Potter, said: "If you have purchased chocolate matching this description, it should not be consumed but instead handed to the police."

Anyone who has developed symptoms or feels unwell after eating the chocolate should seek urgent medical attention from their GP or call 111.