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PARIS — French detectives are still questioning the younger brother of Kim Kardashian West's chauffeur over the robbery of more than $10 million worth of jewelry from the star's Paris apartment in October.

The driver's brother, Gary Madar, 27, and 10 others, including two women, remained in custody Thursday after a round of arrests this week, according to the Paris prosecutor's office.

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Authorities are focusing on the theory that the robbery was an inside job.

The Paris prosecutor's office said chauffeur Michael Madar, 40, was among three people released after being arrested Monday. He is believed to have driven the star on the night of the robbery. A source told NBC News he has been cleared of all suspicion.

Kim Kardashian West attends the 20th Annual Webby Awards in New York. Andy Kropa / AP

Madar and his brother Gary work for the same car service company.

The younger Madar and four other people still in custody are suspected of having a direct role in the robbery, prosecutors said. Investigators have also found the DNA of one suspect, Aomar Ait Khedache, a 60-year-old Algeria-born French citizen, at the scene.

The suspects arrested Monday ranged in age from 23 to 72 and included several people known for prior robberies and other crimes, according to a police document seen by The Associated Press.

Prosecutors told NBC News the younger Madar is suspected of "being in contact with the gang who carried out the burglary in Kim Kardashian West's private apartment in Hotel Pourtales".

Prosecutors believe six people were physically involved in the robbery, with five entering the building and one remaining outside in a car, away from the hotel.

A French investigating judge may travel to the United States to speak with Kardashian West.

The suspects are believed to have forced their way into the private apartment where Kardashian West was staying during Paris Fashion Week, before tying her up and stealing the jewelry. The jewels have not been recovered.