The seven are being investigated for theft, corruption and receiving stolen goods and have been detained since Tuesday.
Other customs officers may be involved in the ring, sources say.
The accused officers, all of whom are experienced but none of whom hold senior positions, allegedly helped themselves to cash from the bags of people suspected of taking drug profits abroad.
Possible links with drug runners are being investigated, according to reports.
The affair came to light during an investigation into an international drug ring when customs officers responsible for surveying and checking baggage were allegedly spotted committing the crimes.
Investigators, working with the utmost discretion, kept tabs on them for several weeks before detaining the suspects.
Economy Minister Pierre Moscovici and Budget Minister Jérôme Cahuzac have promised “exemplary punishment” if the suspects are found guilty.
The customs service, which has 17,500 employees, 1,300 at Charles De Gaulle airport, insists that its workforce is an international byword for integrity and that only 27 of its officers have been fired since 2004.