© Sebastien Salom-Gomis/AFP/Getty ImagesFrench MEP Yannick Jadot said he was 'absolutely scandalised' by the closure of the investigation.
Thirteen children have been born missing hands, forearms or arms in three rural areas of France between 2007 and 2017.
The public health authorities had initially said the incidences of abnormality were "probably down to chance". But doctors at a research organisation said the likelihood of it being coincidental was "more than infinitesimal" and demanded a full investigation.
They believe the clusters may be linked to the use of pesticides and described the French authorities' lack of action as a "health scandal".
Emmanuelle Amar, an epidemiologist and director of the group Remera told the Guardian it would be scientifically remiss not to continue research.
"These malformations are very rare, but also very specific. There is something, some product, that is cutting the limbs at the time the embryo is developing. We must search for it. We must ask ourselves, what could be capable of halting this development and find it."
Amar said the most likely cause of the anomalies was "environmental or medical", but warned against making presumptions. "We have to have a social conscience. These are future children, future generations we are talking about, but they are also individual human dramas," she added.
The phenomenon was first reported near the village of Druillat in the Ain department of eastern France, where seven babies were born without arms, forearms or hands between 2009 and 2014. All lived within a 10.5-mile (17km) radius of the village in an area where maize or sunflowers were cultivated.
Three years later, three children were reported to have been born with similar birth defects between 2007 and 2008 in the town of Mouzeil in the Loire-Atlantique department of western France. In 2015, it was reported a further three children had been born with the same problems in the town of Guidel in Brittany between 2011 and 2013.
The public health authority Santé Publique France said about 150 babies a year in total were born with similar disfigurements in France.
The authority said the situation was "tragic" for the families concerned, but it declared the number of cases in the Ain department to be within the national average. However, it said the Loire-Atlantique and Brittany cases suggested an unusual cluster.
François Bourdillon, the authority's director, said the families involved had been spoken to. "We have listened to their parents and their grandparents and visited their homes. No environmental factor - pesticides, for example - can be blamed," he said. "We have not identified a common exposure to the occurrence of these malformations."
In a statement, Santé Publique France said it had closed its investigation into the cases. "The absence of a hypothesis of a possible common cause does not make it possible to hold further investigations," it said.
Amar said the authority's conclusion was not acceptable and that the number of babies born with similar disfigurements in the Ain department was "58 times higher than what we would normally expect". "We're saying to families that they'll have to live with questions and that it's just bad luck," she said.
Remera said it had carried out its own investigation into the cases in the Ain, speaking to the mothers concerned to establish if there were any common factors. They have ruled out genetic causes as well as links to medication, food or alcohol consumed during pregnancies. They found no pattern of behaviour among the mothers.
"We interviewed all the mothers with a very extensive questionnaire on their lifestyle. The only thing they have in common is that they all live in a very rural area."
Possible links to agriculture have been bolstered by reports that several calves were born missing tails and ribs at Chalamont, another village in the Ain department, at the time the cluster of disfigured babies occurred.
"It is believed that this revolves around agriculture," Amar said, adding that it was vital for national health officials to launch a full investigation. She said Remera was facing funding cuts and could not continue looking into the clusters on its own.
Céline Figueiredo, whose four-year-old son Sacha was born in the Ain without a hand, said: "I am outraged that no investigation has yet been launched. We have the means in France to investigate the causes of these malformations. They must try to give us answers rather than cover up the cases."
Yannick Jadot, a former Green party presidential candidate and member of the European parliament, said he was "absolutely scandalised". "What we seem to be ignoring is that it's very likely these malformations are linked to pesticides," he told RTL radio.
"We have never wanted to know in France; we don't want to do epidemiology studies around [waste] incinerators, around nuclear power stations, or on pesticides, because, once again, we don't want to know."
Comment: It's highly possible that industrial agro-chemicals are to blame, see: