Tests showed that 12 soldiers had used cannabis and five of them had traces of cocaine, he said.
The Swiss army has 4,500 troops on duty at the WEF.
Mr Hofer said it was important that soldiers were fit for duty and safe to drive.
The soldiers found to have used cocaine had been sent home and would face further disciplinary measures, he said.
One of them was found in possession of 3 grams of cocaine and will face a criminal investigation by civilian authorities.
The remaining seven soldiers will face disciplinary measures while remaining in post at Davos, as cannabis use is a lesser offence.
The unit concerned is made up predominately of soldiers from the cantons of Ticino and Graubuenden.
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