Francois Bourdillon, head of the Public Health France agency, confirmed for the first time that a national investigation was “underway” and the results would be known in about three months.
Confidence in the state's handling of the issue took a blow Monday night when health authorities reported an additional 11 cases in the Ain area near the Swiss border between 2000 and 2014 which had not previously been made public.
A relatively small number of cases have been detected so far in total — about 25 over the past 15 years in the regions of Brittany, Loire-Atlantique and Ain — but the defects have caused public alarm and have been widely reported by the French media.
Officials had already called the number of cases in Brittany and the Loire-Atlantique areas, on France's west coast, statistically “excessive” and Health Minister Agnes Buzyn has vowed to investigate further.
So far, no explanation has been found for the deformations despite tests on the mothers to see if they were exposed to common substances.
Some environmentalists have claimed pesticides or other chemicals could be to blame — the cases are clustered in rural areas — but there is no evidence at this point to back up the claims.
The defects could also be genetic.
The incidents of babies born without arms was brought to public attention by a scientist at the Remera public health body, which was created after the thalidomide scandal and is responsible for tracking birth defects.
The scientist, Emmanuelle Amar, has been hailed as a whistleblower by ecologists and campaigners, but has been attacked for scare-mongering by others, including fellow scientists.