Some 450 first-year fraternity students from Utrecht have cut short their skiing holiday in the French resort of Risoul because they they were hit by a mysterious illness following an evening out.

A total of nine students fell ill on two consecutive nights, and five had to be taken to hospital. Panic attacks, shaking, weak legs and short-term memory loss were among the symptoms they experienced, and so far no-one has come up with the cause.

Both men and women were affected, about half and half, a spokesman for the fraternities told NU.nl. All the students have since been discharged from hospital.

The bar where the students partied has been mentioned in connection with the incidents and local rumour has it that the drug GHB ended up in their drinks.

News website Nu.nl quotes a letter from the fraternity boards which say the students  ‘distrusted’ the bar staff, security staff and other groups of holiday makers. The bar owners have denied any involvement, stating that no proof of GHB poisoning has yet been found.

The results of the blood tests are expected in a few days.