A group of 13 metal detectorists were taken to hospital after they reportedly fell ill from eating a birthday cake spiked with cannabis.
The chocolate cake was handed out at a metal detecting festival in the village of High Melton, Yorkshire, on Saturday.
It was reported that a man gave out pieces of his 50th birthday cake, not knowing it had been laced with cannabis.
Thirteen people from across the country were taken to hospital by Yorkshire Ambulance Service from the Coil to the Soil event after falling ill. Another two people were treated at the scene.
A spokesman for South Yorkshire Police said a 48-year-old woman from County Durham had been arrested and bailed in connection with the incident.
A police spokesperson said: "An investigation is under way after a group of people fell ill as a result of eating something reportedly containing cannabis, during an event in the High Melton area of Doncaster.
"The group, of both men and women, were taken to hospital at about 7pm on Saturday 24 August. All have since been discharged.”
Members of the metal detecting community expressed their disgust at the incident.
Julian Evan-Hart, editor of Treasure Hunting Magazine, said it was a "dreadful incident" but he did not believe it was malicious.
"I think it was an irresponsible, poorly thought-through joke," he said.
"This isn't a poor reflection on our hobby, the dig organisers or anyone else involved the planning of the event. It's just a case of random lunacy."
A Yorkshire Ambulance Service spokesman said 15 patients were treated by ambulance service staff on the scene and 13 of those were taken to hospitals in South Yorkshire for further care.
The spokesman said: "Yorkshire Ambulance Service received an emergency call just before 6.30pm on Saturday 24 August 2019 to reports of a number of people feeling unwell at a national metal detecting event being held near Sprotbrough, Doncaster in South Yorkshire.
"They had become unwell after ingesting an unknown substance.
"Eight ambulances, a rapid response vehicle, two doctors, two clinical supervisors and the Trust’s Hazardous Area Response Team (HART) were dispatched to the scene.
"Fifteen patients were treated by ambulance service staff on scene and 13 of those were conveyed to hospitals in South Yorkshire for further care."