Marseille state prosecutor Dominique Laurens confirmed to Agence France-Presse that an investigation is underway, and the international Cycling UNion has said it "welcomes" the inquiry. 

It relates to the "discovery of many health products including drugs... and especially a method that can be qualified as doping", Laurens said.

The investigation concerns the Arkéa-Samsic team and Le Parisien claims a doctor and a physiotherapist were detained by police for questioning. 

Arkéa-Samsic's leading rider, Nairo Quintana, was among those to have his hotel room searched in a police raid last Wednesday (September 16).

Officers from the Central Office for the Fight against Environmental and Public Health Damage (OCLAESP) conducted the search.

Saline and injection equipment were said to have been found.

Colombian Quintana is a former winner of two Grand Tours, the 2014 Giro d'Italia and 2016 Vuelta a España.

He finished 17th in the general classification of this year's Tour de France, which concluded yesterday with 22-year-old Tadej Pogačar of Slovenia capturing the yellow jersey.

Quintana has twice before been the Tour de France runner-up.

The rooms of Quintana's brother, Dayer, and compatriot Winner Anacona - both Arkéa-Samsic team mates - were also searched, per the L'Équipe report on the raid.

A UCI statement on the matter said: "The UCI confirms that it has been in communication with the OCLAESP and the Cycling Anti-Doping Foundation as part of the legal operations carried out by the French authorities on the sidelines of the Tour de France. 

"The UCI welcomes and supports the action of all parties involved and will take the appropriate measures once it has taken note of the information obtained by the French legal authorities."