He was arrested by the direct orders of Louvois on 5 December 1677, after having declared that he was able to make gold and had been observed with a banknote of 200,000 livres.
In connection to his arrest, his valet La Chaboissiere and the banker Pierre Cadelan, who signed the banknote, were taken into custody.
It was known that Chaboissiere had visited Abbé Nail, an accomplice of the poisoner Magdelaine de La Grange, in prison.
On May 17, 1678, the nobleman Robert de Bachimont and his wife, Marie, were arrested in Lyon for their connection to Vanens.
Vanens was imprisoned in the Bastille for several years without trial during the Poison Affair while the police waited for evidence to incriminate him.
He was accused of having sold mixtures to prolong love, affect marriages, and find lost treasures.