PARIS, Jan. 17 (Xinhua) -- The man who was left brain-dead after a botched drug test in Rennes in northwest France died on Sunday, the regional hospital center CHR announced Sunday afternoon.

Five other volunteers taking part of the test of an oral medication were in stable situation, Rennes hospital, where they have been treated, added in a statement.

All the volunteers are men aged between 28 and 49 years.

Prosecutors have opened an investigation into the "unprecedented and serious accident," according to French Health minister Marisol Touraine.

In a press meeting held on Saturday, Touraine noted the experimental medicine, manufactured by Portugal-based Bial lab dealt with pain by acting on the body's endocannabinoid system.