LONDON, United Kingdom (AFP) — A court in England on Friday jailed a man for more than 31 years for drugging and sexually abusing young boys at a Christian summer camp he led last summer.

Police say they are now talking to other groups he worked with in the past as part of an ongoing investigation.

Former vet Jon Ruben, 76, was leading the camp last July, said a statement from prosecutors released after Friday’s judgement.

He laced sweets with sedatives and tricked children at the camp into eating them by encouraging them to take part in a game.

READ: 76-y-o man before court, accused of lacing sweets at kids camp

“Later on, while the boys were heavily asleep, he went into their dormitory and chose individual boys to sexually abuse them,” said prosecutors.

Volunteers at the camp in Leicestershire, central England, raised the alarm after finding the children still nauseous, drowsy and disoriented the next day.

Eight boys aged between eight and 11 were taken to hospital and Ruben was arrested.

Investigators found syringes and sedatives at the camp location.

On his devices, they found indecent images of children as well as evidence that he had procured tranquiliser drugs and tried to join an online paedophile network.

Ruben admitted offences relating to ill-treatment of children and sexual abuse — as well as to drugging his wife, who was volunteering at the camp, in order to avoid detection.

A court in Leicester sentenced him on Friday to a total of 31 years and 10 months behind bars under special provisions for defendants designated by prosecutors as particularly dangerous.

Leicestershire police said the investigation into Ruben was still “very much ongoing”.

Officers are contacting schools and youth organisations in central England with which Ruben was involved over the past two decades