French Health Minister Marisol Touraine, left, and Professor Gilles Edan, the chief neuroscientist at Rennes Hospital, address the media at a news conference Friday. (David Vincent/AP)

Six people were hospitalized in France — including one person who was brain dead — after participating in a clinical drug trial, the French health ministry said Friday.

Officials learned of the serious "accident" in the Phase 1 clinical trial Thursday night, according to the French Ministry of Social Affairs, Health, and Women’s Rights.

"This is unprecedented," French Health Minister Marisol Touraine said at a news conference, according to Reuters. "We'll do everything to understand what happened."

The six volunteers were hospitalized in Rennes, a city in western France; they had been taking an oral medication that is being developed by a European lab, the health ministry said.

The trial was focused on a "new painkiller compound," according to the Associated Press, which reported that the drug was being manufactured by Bial, a Portuguese company.

"Several BIAL representatives are currently at the site to monitor the situation with the research center and the hospital, ensuring the necessary cooperation with these entities, as well as with the relevant authorities," Bial said in a statement, which said five volunteers were hospitalized, not six.

The drug had already been given to 108 patients "without any moderate or serious adverse reaction," Bial said.

"Together with all the relevant authorities, BIAL is strongly committed to  ensuring, first of all, the well-being of all participants in this trial and to determine thoroughly and exhaustively the causes which are at the origin of this situation," BIAL's statement said.

According to AP, Touraine said the medication at the center of the clinical trial is not based on cannabis, as some reports had claimed. Touraine, the wire service reported, "urged calm, saying that no drug currently on the market was implicated in the failed trial."

The hospitalized volunteers are all men ages 28 to 49, Touraine said, according to Reuters, which reported:

The six men started taking the drug on Jan. 7. The brain-dead volunteer was admitted to hospital on Monday, the minister said.

For three of the five others - who went in on Wednesday and Thursday - there are fears of irreversible handicap, doctor Gilles Edan said, though he still hoped that would not be the case. One of the six had no symptoms but was being carefully monitored, he said.

The trial has been suspended, according to the health ministry, and the volunteers who participated in it are being recalled.

The New York Times reported that Biotrial, a drug evaluation company, was conducting the trial. Biotrial released a statement saying that "serious adverse events related to the test drug have occurred in some subjects" of a study.

"The trial has been conducted in full compliance with the international regulations and Biotrial’s procedures were followed at every stage throughout the trial, in particular the emergency procedures for the transfer of subjects to the hospital," the statement said. "We are in close and regular contact with the Health Authorities and Ministry in France.

"The priority at Biotrial remains the safety of our subjects. We are very grateful for the support we have been receiving from our clients and partners today."

William Wan and Frances Stead Sellers contributed to this report, which has been updated.

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