At least six people are critically ill in France after a trial involving a new medical treatment went wrong, the French health ministry said.

The patients became ill and were admitted to hospital earlier this week after taking a trial drug developed by a private medical laboratory in the northern city of Rennes, the French TV channel TF1 said on Friday.

"This test was carried out at a private facility specialised in carrying out clinical trials," the ministry said in a statement.

One of those affected was described by the health ministry as being "in a state of clinical death".

Calling it a "grave accident", the ministry said that Marisol Touraine, France's health minister, would travel to Rennes, where the trial was taking place, on Friday afternoon.

French media outlet BFMTV said eight people were believed to have taken part in the trial, with two of those given placebos. In total, 90 people have taken part in the trial.

All trials on the drug have been suspended and all volunteers who have taken part in the trial are being called back.

Another media outlet, iTele, said that the trial was for a painkiller containing cannabis and took place at a laboratory in Rennes.

Source: Al Jazeera and agencies