Story highlights Bial says drug was already given to 108 people with no "serious adverse reaction"

The drug was being tested to help people with anxiety disorders and motor skills issues

The French Health Ministry is investigating what went wrong

(CNN) One person has been declared brain dead and five others are hospitalized in France after they participated in an early stage clinical trial for a new drug, French health officials said Friday.

The French Health Ministry is investigating what it calls a "serious accident."

Four of the patients may be permanently disabled with neurological damage, doctors in the northwestern city of Rennes said. One other person doesn't have symptoms but remains under medical surveillance.

The company conducting the testing said on its website the trial was administered "in full compliance with the international regulations and Biotrial's procedures were followed at every stage throughout the trial."

Biotrial International said it was "in close and regular contact with the Health Authorities and Ministry in France."

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