Five people were taken to hospital after eating a cake laced with cannabis at a steam engine fair.
One woman collapsed after eating the cake, which was served up by a group of exhibitors at the Bluebell Railway Steam Fair, Horsted Keynes, on Saturday.
The five victims, all from Sussex, had no idea the cake was spiked.
They were taken to the Princess Royal Hospital, Haywards Heath, complaining of hallucinations, fits and sickness, after police and an ambulance arrived on the scene.
A 54-year-old man from the Fairlight area was arrested on suspicion of supplying cannabis and was released on police bail.
A volunteer at the fair said he thought it was a joke that backfired.
Yesterday, hundreds of families flocked to see the vintage engines and classic cars on display at the show, oblivious to the events of the day before.
Tim Baker, marketing manager of the steam fair, said the "hash-cake" incident had come as a shock and added: "We have been doing this for eight years and nothing like this has ever happened before.
"This show is all done by volunteers and it has knocked back their morale a bit."
Mr Baker said the cake was brought on site by a group of people exhibiting vintage motorbikes in the top field.
He said: "It was eaten at some kind of a birthday party in the marquee. The first we knew about it was when one woman collapsed.
"The group left this morning and they will not be coming back. Their cards are marked."
Sgt Jim Casey, of Haywards Heath police, said the residue of the cannabis-laced cake will be sent away for analysis.
All of the victims have now been released from hospital.
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