Kim Kardashian West participates in a television interview as she arrives for the 20th Annual Webby Awards in Manhattan, New York, U.S., May 16, 2016. REUTERS/Mike Segar/File Photo

PARIS (Reuters) - The Paris prosecutor has placed four people suspected of involvement in the armed robbery of U.S. reality television star Kim Kardashian under formal investigation, the prosecutor’s office said on Thursday.

A spokesman for the office said the four - aged between 27 and 64 - were being investigated for armed robbery as part of an organized gang and for kidnapping or sequestration. They will remain in provisional detention.

Six more people could also be put under formal investigation on Friday, the prosecutor’s office said.

On Monday, police investigating the robbery arrested 17 people, including a chauffeur who drove Kardashian around Paris in the days before the robbery.

In the early hours of Oct. 3, thieves wearing balaclavas and police jackets burst into the luxury property in central Paris where Kardashian, who is married to U.S. rapper Kanye West, was sleeping.

They tied her up at gunpoint before making off on bicycles with her engagement ring and other jewels worth 9 million euros ($9.5 million), authorities said at the time.