French authorities arrested a 22-year-old on Wednesday as part of an investigation into a hack of the country’s Interior Ministry that saw the perpetrators access several email accounts and dozens of confidential documents.

The ministry confirmed what was described as a serious incident after a user claimed credit for a hack on the cybercrime website BreachForums. A government spokesperson said the “reality and scope” of that post “are currently being subjected to in-depth verification as part of the investigation.”

Interior Minister Laurent Nuñez told journalists the hack last week compromised files relating to judicial records and wanted persons. He said the hackers had been in the network for several days.

Nuñez could not “absolutely say whether this will compromise investigations or not,” but stressed that the ministry had not received a ransom demand and that the attack “does not endanger the lives of our fellow citizens.”

Officials said the incident is being handled “with the highest vigilance and at the highest level” because of the sensitivity of the systems involved.

In an announcement on social media, the Paris Prosecutor’s Office said a person had been arrested on charges “including an attack on an automated personal data processing system operated by the State, as part of an organized group.”

The offence carries a potential sentence of 10 years in prison.

Prosecutors say the suspect, born in 2003, was already known to them after having been convicted of similar crimes earlier this year. They said an update would be provided at the suspect’s time in police custody, which could last up to 48 hours.