PARIS (AP) — Five men hospitalized after taking part in an experimental drug test that killed another volunteer are improving, with one returning home, a doctor announced on Monday.

A day after the death of one of the 90 previously healthy volunteers in Rennes, Dr. Gilles Brassier said that three people are now being cared for by neurology services at hospitals near their homes. The other is hospitalized in Rennes.

French health authorities said on Friday that three of the five hospitalized volunteers may suffer brain damage. It was not immediately clear whether Monday's upbeat report on the five means officials were overly pessimistic last week. Brassier said there would be no comments after his brief report.

The trials were stopped after six people became seriously ill. One suffered brain death and died on Sunday.

Brassier, head of Rennes University Hospital's medical commission, announced that neither clinical nor radiological anomalies were found in 18 other volunteers checked so far. The hospital is arranging to test all those involved in the drug trial, which was in its first phase.

The trial, which began Jan. 7, involved 90 healthy volunteers who were given the experimental drug orally in varying doses at different times.

The trials were carried out by the Rennes-based Biotrial company for the Portuguese pharmaceutical company Bial on a drug that Health Minister Marisol Touraine said was being developed to treat pain, ease mood and anxiety troubles as well as motor problems linked to neurodegenerative illnesses

It's rare for volunteers to fall seriously ill during Phase 1 trials, which study safe usage, side effects and other measures on healthy volunteers, rather than drug effectiveness.