Two people from Lyon have been charged on suspicion of selling more than 1,000 fake COVID-19 health passes.
The couple are accused of hacking into a French nurse's account in Gironde last summer to create the forged certificates.
They were arrested on Tuesday after "several months" of investigations, the Bordeaux public prosecutor's office said.
The case was initially launched after a private practising nurse discovered that their professional account dedicated to COVID-19 vaccines had been hacked.
The hackers "generated more than a thousand false health passes in a few days", police said in a statement.
They had used "anonymous software" to access the nurse's records at a clinic in Le Taillan-Médoc, they added.
The cyberattack was traced to a couple living on the outskirts of Lyon, where police also seized a handgun, €9,000 euros, around 20 mobile phones, and "a very large number of digital media".
A male suspect has been held in custody while his partner was released under judicial supervision, prosecutors added.
In December, France's interior ministry said police had detected 182,000 fake COVID passes since they were introduced in the summer.
On Thursday, France's Prime Minister announced that the country would introduce a new "vaccine pass" on Monday.
Citizens will need to be fully vaccinated or have recently recovered from infection to enter bars, restaurants, and other cultural venues.