Dutch doctors are concerned about a higher than expected mortality rate in a clinical trial to treat patients with acute inflammation of the pancreas.
Out of a group of 296 patients, 24 who took probiotic bacteria died. The research was carried out in 2004-2007.
Probiotics are living bacteria used in the treatment of intestinal complaints.
The exact cause of death has not yet been identified. In a comparable group of patients who had conventional treatment, only nine died.
The pancreatitis research was spearheaded by the University Medical Centre in Utrecht.
The bacteria involved in the research were varieties of Lactobacillus, Enterococcus, or Bifidobacterium, Radio Netherlands reports.
The Utrecht researchers said no unorthodox procedures had been used.
They added that results of earlier and smaller tests in other countries had shown that administering probiotics would lessen inflammations of the pancreas.
All the patients had signed a declaration confirming their willingness to participate in the trials.