Bial said it is working with health authorities to understand the causes of this tragic and unfortunate situation.
The yet to be named drug, believed to be BIA 10-2474, is an inhibitor of fatty acid amide hydrolase.
Under the trial, which started earlier this month, 90 healthy volunteers were given the drug in several doses at different times.
The hospital said it has contacted the 84 other volunteers exposed to the drug. Ten of those volunteers underwent medical exams, but the hospital found no anomalies.
It said another five will have medical exams closer to their homes, but did not tell whether the others are being monitored or tested.
French health minister Marisol Touraine has pledged to get to the bottom of what she called a tragic accident.
After visiting volunteers who took part in the trial, she told reporters: "I was overwhelmed by their distress. Their lives have been brutally turned upside down."