French authorities have taken into custody two managers of the online taxi-booking service Uber, over "illicit activity" involving its service.
Monday's detentions and questioning came amid rising tensions between the government and the company, which culminated last week in a violence-marred taxi strike that blocked roads around the country.
Related: Uber beefs up security after hacking scare
In 2014, an investigation was opened into Uber's application which is used to put paying clients in contact with cheaper, private drivers who do not face the same regulations as licensed taxi drivers.
French authorities are frustrated that Uber does not pay the same taxes and social charges as traditional taxis, whose drivers have lashed out against what they see as unfair competition.
Uber, meanwhile, argues that the French system is outdated and needs reform to keep up with apps and geo-localisation.
Uber did not immediately respond to a request for comment on Monday, but officials last week vowed to keep operating its budget UberPop service until France's top court rules on its use.
A spot check of the application on Monday showed drivers available in central Paris.
Agnes Thibault-Lecuivre, the Paris prosecutor's spokeswoman, did not name the two Uber managers detained on Monday.
The standoff reflects larger tensions in France over how to regulate fast-moving technology and stay globally competitive while ensuring labour protections.
Uber has also run into legal problems elsewhere in Europe, as well as in China and India.