Four baggage handlers from Charles de Gaulle airport outside Paris who lost their clearance filed a joint discrimination complaint this week, alleging they had been unfairly associated with terrorism because they are Muslims, their lawyers said on Friday.
Some had been in their jobs for up to five years.
The staff lost their security clearances - which allowed them to work in sensitive airport customs zones - because France's Anti-terrorist Co-ordination Unit (UCLAT), as part of an 18-month investigation, said they posed "a risk to the airport's security" or were simply deemed "dangerous", said Jacques Lebrot, the airport's deputy chief of police.
"The fact of being a practising Muslim was absolutely not a criteria" for suspending the workers' clearance, Lebrot added.
The decision came from the Seine-Saint-Denis police district where the airport is located.
Lawyers and community groups said the baggage handlers, who worked for subcontractors at the airport, were likely to lose their jobs because such work depended on security clearances.
"You don't strip people of their badges for small matters," Lebrot said. The crackdown was part of heightened security in France, after terror attacks in Britain, Spain and the US in recent years.
Lebrot, citing security reasons, declined to say whether the "several dozen" people - he would not specify how many - who lost their badges had been involved in specific plots.
"Mr X or Y could have been suspected because corresponding facts ... suggested he belonged to a sizable network," Lebrot said, without elaborating. Others could have been stripped of the badges because they were "impressionable and manipulated" by such networks, he said.
In letters from the regional government office, the employees were told that they presented a "significant danger to airport security", or had shown "personal behaviour threatening airport security".
Lawyers for those who lost their badges said that under police questioning, they were never told of the reasons they lost their badges - but repeatedly asked about their religion.
"The link among these people is that either they are Arab - or practise their religion in a normal way," said Eric Moutet, a lawyer for the four employees suing in administrative court. Authorities, he said, "are in essence asking people to prove they are not terrorists".
During the inquiry before a suspension, a worker may be asked about his behaviour and religious practices, the official said.
He gave the example of airport workers who lost their badges because they had attended Islamic schools deemed dangerous in Pakistan and Afghanistan.
Security fears involving workers at the Charles de Gaulle airport have been raised before, and a book claiming the airport was infiltrated by Muslim militants stirred a furore when it was published in April.
Anti-terrorist officials cast doubts on claims made in The Mosques of Roissy, by right-wing French politician Philippe de Villiers.
And an airport union, Sud Aerien, accused Villiers - a presidential hopeful in next year's elections - of playing on public fears of Islamic radicals to win votes.
In 2002, a French-Algerian airport baggage handler was arrested when weapons and explosives were found in his car. Police later said he had been the victim of a set-up.