The oral trial was being conducted by a private laboratory in the north-western city of Rennes, Marisol Touraine said. The trial has been suspended and the firm is recalling the volunteers. It is unclear how many people are involved.

Media reports that the drug is a cannabis-based painkiller have been denied by the health ministry. The Paris prosecutor's office said an investigation had been opened. The drug was taken in a licensed laboratory, the ministry said in a statement (in French).The study was a Phase I clinical trial, in which healthy volunteers take the medication to evaluate the safety of its use, the ministry said.

Phase I tests for safety
A small number of people, sometimes healthy, and sometimes with a medical condition, are given a tiny dose of the drug under careful supervision, not to test if the drug works, but in order to check for any side effects

Phase II
Sees the drug given to people who have a medical condition to see if it does indeed help them Phase III Trials are only for medicines or devices that have already passed the first two stages, and involve them being compared to existing treatments or a placebo. The trials often last a year or more, involving several thousand patients