Six people are in a critical condition – including one in a coma – after clinical trial of new drug in France, the country’s health minister says.
Marisol Touraine said there had been a “very serious accident” during a trial by a private laboratory in Rennes.
The minister said she would be making an emergency visit to the city, in the north-west of France, on Friday.
The trial has been suspended and the firm is recalling the volunteers. It is unclear how many people are involved.
Participants had taken “a drug taken orally being developed by a European laboratory” that was licensed to operate, the ministry said in a statement (in French).
Unconfirmed French media reports said it was a cannabis-based painkiller.
The first people to fall ill were taken into hospital earlier this week, French media said. An investigation is under way.
Ms Touraine expressed her “deep determination to get to the bottom… of this tragic accident” and find who was responsible.