The woman filed a rape complaint after going to the fire station in the 14th district in the southeast of Paris on Friday evening after meeting a fireman in a bar.
She told investigators that she had agreed to consensual sex with him and he is not considered a suspect.
But she alleges that several other men then raped her.
Not all of the six suspects, aged between 23 and 35, are set to be charged with rape. Some will face charges of failing to report a crime when they are presented to a judge later on Monday, two legal sources told AFP.
The allegations come three weeks after the Paris fire service was hailed for its bravery and professionalism for bringing a huge blaze at the Notre-Dame Cathedral under control.
The case echoes another gang-rape scandal involving the French emergency services which saw two police officers sentenced to seven years in prison in February for the rape of a Canadian tourist at Paris police headquarters.