The press freedom watchdog group also says it has become a civil party to the investigation.
De Bourgues was found dead on August 2 in the apartment he was renting in Almaty, the former capital of Kazakhstan.
De Bourgues was in Almaty to prepare a report on Kazakhstan for SML Strategic Media, a U.S.-based media-consultancy group.
Kazakh authorities say burglars are responsible for the killing. But Kazakh media watchdogs suspect foul play.
RSF representatives traveled to Kazakhstan in September to investigate De Bourgues' death.
RFE/RL Central Asia Report
RFE/RL Central Asia Report
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