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 reportedly been suspended and the volunteers involved recalled.
