BERLIN (AP) — Authorities say emergency workers called to a conference center in northern Germany found some 30 people staggering and suffering from cramps, apparently as a result of amphetamine poisoning.

The local government said 15 ambulances and a helicopter were sent to the scene Friday in the small town of Handeloh, south of Hamburg, the dpa news agency reported.

Fire service spokesman Matthias Koehlbrandt told broadcaster NDR the group was aged between 25 and 55. NDR reported they were alternative and homeopathic practitioners, and that they were taken to the hospital.

Authorities said their preliminary finding was that the group was poisoned with amphetamines, but Koehlbrandt said they didn't knowingly take the substance.