The visit, which Algiers finally agreed to allow last month, is intended to be the first of many and is meant to set the guidelines for more to come, sources say.
Investigators want to perform an autopsy on the heads of the seven Cistercian monks, which were found by the side of a road two months after they had beeen kidnapped from their isolated monestery at Tibéhrine in northern Algeria in March 1996, and to interview witnesses.
Djamel Zitouni, the leader of the Armed Islamic Group (GIA), which was locked in combat with the Algerian army, claimed responsibility for both the kidnapping and the murders.
But there have long been rumours that Zitouni was an agent of the Algerian secret services and investigators want to look into suggestions that the deaths resulted from a blunder by the Algerian armed forces.
Trévidic was to return to France on Wednesday.
The monks' lives leading up to their kidnapping was the subject of popular French film, Of Gods and Men, released in 2010.