France's health minister has ordered a fresh investigation into why 14 babies in rural areas were born with missing limbs in recent years, saying it was "unacceptable" that previous probes had not got to the bottom of the mystery.

The announcement came just two weeks after an inquiry by health authorities ended with doctors saying they had failed to find out what had caused the babies to be born with stunted or missing arms since 2007.

“We cannot simply say that we didn’t find any causes, that is unacceptable,” Health Minister Agnes Buzyn told RTL radio.

The cases were found in three different clusters - in the Ain department near the Swiss border, which had seven cases between 2009 and 2014, Brittany, which had four cases between 2011 and 2013, and Loire-Atlantique, south of Brittany, which had three cases in 2007-2008.

Ms Buzyn said the new inquiry would be led by her health ministry and the department of environment in order to combine medical and environmental expertise.

Pesticides used by farmers were the most likely cause for the abnormalities, according to doctors at research organisation Remera, which monitors the incidence of birth defects in one French region.