Marisol Touraine, France's Health Minister
France's Health Minister, Marisol Touraine is planning an emergency visit Rennes, in France as soon as possible.Getty Images

A "serious accident" has taken place during a Phase 1 clinical trial in France, leaving one person dead and five more in a critical condition. The drug was being tested at a private clinic in Rennes, with early reports saying it was a trial by Biotrial, a French company that employs 300 people worldwide.

France's minister of health, Marisol Touraine, said a "very serious accident" had taken place and that the study had been halted, with all volunteers recalled. "This trial was performed in a licensed private institution specialising in the conduct of clinical trials... in healthy volunteers. This accident caused the hospitalisation of six of the volunteers at the University Hospital of Rennes. One of them in intensive care, is brain dead," a statement said.

Touraine is due to hold a press conference later on 15 January. She said she is determined to "get to the bottom and establish all responsibilities in this tragic accident".

What was the drug being trialled?

Initial reports into the clinical trial suggested it was a cannabis-based painkiller. A source close to the case told AFP the drug was a painkiller containing cannabinoids, an active ingredient found in cannabis plants. However, this has been disputed. A spokesperson for France's health ministry told The Local these claims had been false.

The drug being tested was an oral medication currently being developed by a "European laboratory". It is thought the drug being tested was for pain relief. According to Oust France, the trial involved eight volunteers. Six of the participants were given the drug, while the other two were given a placebo.

Reports indicate the condition of the participants worsened throughout the week. The first was taken to hospital on 11 January and they are now being treated in the neurology department. They are aged between 30 and 50 years.

Other than this, little is known about the drug involved. Further updates are expected as the investigation continues.

Phase 1 clinical trials are designed to test the safety of a new drug. While severe reactions to the medication are rare, they do happen. In 2006, six men were in hospital after taking a drug designed to fight auto-immune disease and leukaemia. Within hours of taking it, they experienced organ failure. While none died, all were later told they would likely develop cancers and disease as a result of being exposed to the drug.

Biotrial, which has not been confirmed as the company carrying out the trial, is yet to comment on the incident.