A French court on Wednesday acquitted all six defendants on trial over the distribution in the 1980s of growth hormones contaminated with the fatal Creutzfeldt-Jakob disease (CJD).

The court ruled it was impossible to be certain the doctors and pharmacists on trial were aware of the risk of contamination by CJD, which was little known at the time.

The brain-wasting disease causes rapid dementia and death and most of the 117 infected victims so far have been children. The three most recent deaths occurred in 2008.

The trial began on Feb. 6 last year after a 17-year investigation. The doctors and pharmacists were facing charges of aggravated deception, manslaughter and causing unintentional injury.

In May, prosecutors said three of them should be acquitted while four should go to jail. One of the four has since died.

Bernard Fau, a lawyer representing the families of victims, said he would ask Justice Minister Rachida Dati to request an appeal. The families cannot launch an appeal themselves but Dati can ask prosecutors to do so.

"The justice system has killed all the victims all over again, it's like a second bereavement for us. It's terrible for parents, husbands, wives," said Jeanne Goerrian, head of an association representing the families.

The case, which carries echoes of a separate scandal over HIV-contaminated blood transfusions in the 1980s, centres on a programme to treat children of short stature with growth hormones extracted from human pituitary glands.

The defendants admitted making mistakes, but they argued the risks connected with the treatment were not known at the time.

Luc Montagnier, the Nobel Prize-winning scientist who identified the AIDS virus, told the court last year he had warned colleagues at the Pasteur Institute in 1980 that the hormone they were extracting could carry CJD.

The defendants included Jean-Claude Job, former president of the France-Hypophyse association and Fernand Dray, former head of a research unit at the prestigious Pasteur Institute. Job died in October aged 86.

Investigators found evidence that France-Hypophyse, which had a monopoly on collecting and distributing pituitary glands from corpses in France and eastern Europe, often worked in unhygienic conditions.

The radio-immunology unit at the Pasteur Institute, which extracted the hormones from the glands, was also accused of sloppiness in handling, transporting and stocking the material.

Half of the 120,000 organs acquired in 1983-88 for sums of between 35 and 50 francs (5-7 euros) came from corpses in Bulgaria and Hungary, many from neurological or infectious wards.