France, May 3 -- Prosecutors said Saturday that 21 suspects in a series of coordinated attacks on French prisons had been charged, including two teenagers.

Investigators believe the attacks were carried out by drug traffickers, with at least one suspect thought to have ties to a notorious cartel.

Attackers in April struck at several jails and other facilities across France, torching cars, spraying the entrance of one prison with automatic gunfire and leaving mysterious inscriptions.

A total of 30 people, including four minors, were arrested this week in police raids across France. Seven of them were released without charge.

Paris prosecutor Laure Beccuau told reporters Saturday that 19 of the suspects were being held in pre-trial cust...