Thirteen people were taken to hospital when they fell ill after reportedly eating a 50th birthday cake laced with cannabis - at a metal detecting convention.
Police are investigating after the group became unwell, dancing, laughing and some collapsing, after eating the cake during a weekend rally in Yorkshire on Saturday without realising it contained the drug.
According to social media, a chocolate cake was baked for a man who was attending the event and celebrating his birthday.
He had not realised the cake contained cannabis.
Thirteen people were taken to hospital by Yorkshire Ambulance Service from the Coil to the Soil event in High Melton, Doncaster. Two others were treated at the scene.
South Yorkshire Police said a 48-year-old woman from County Durham was arrested in connection with the incident.
A police spokesperson said: "An investigation is underway 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.
"A 48-year-old woman from County Durham has been arrested in connection to the incident and currently remains in police custody where she will be spoken to by detectives."
A Yorkshire Ambulance spokesman said people 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," he said.
"Fifteen patients were treated by ambulance service staff on scene and 13 of those were conveyed to hospitals in South Yorkshire for further care."
