A federal grand jury has indicted 11 people for possession of machine guns or small devices to convert semiautomatic weapons to fully automatic, officials announced on Friday.

Jonathan S. Ross, acting U.S. Attorney for the Middle District of Alabama, announced the arrests at a news conference. Officials said they hope the announcement and the prosecutions can deter what they said has been a growing threat to public safety and law enforcement. They said the small machine gun conversion devices, or Glock switches, are readily obtainable.

“Our goal today is to get the word out that, one, these devices are illegal,” Ross said. “They’re illegal in and of themselves. Federal law considers the device itself to be a machine gun and possession of it is punishable by up to 10 years in prison. We want to get that word out. And these prosecutions, our hope is that they will have a deterrent effect.”

Ashley Lightner of the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) said Glock switches allow a semiautomatic handgun to fire 20 rounds in one second.

“It converts a perfectly good semiautomatic pistol into a machine gun capable of firing at a machine gun rate,” Lightner said. . “These are dangerous. They’re being used in our community. They’re being used in violent crime and we’re seeing them connected to shootings in our community.”

Lightner said it takes only about 15 minutes to make a Glock switch on a 3-D printer. He said it takes about a minute to attach one to a gun.

At the news conference, officials showed a video demonstrating the difference between firing a semiautomatic handgun and firing one with a Glock switch. Lightner said the converted weapons are more dangerous not only because of the increased firepower but also because they make the guns inaccurate.

“A person shooting a semiautomatic pistol can shoot a tight group (on a target) and be very accurate with it,” Lightner said. “Even a person who’s really good at shooting and has a pistol that has a Glock switch on it, it’s going to ride up on him. It’s not accurate.”

“There’s a good chance that innocent bystanders are going to get shot with that pistol because of the inaccuracy of it,” Lightner said. “And we’ve seen that across the nation. We’ve seen that here in Alabama in shootings, where innocent individuals have been shot.”

The 11 indictments announced Monday are for crimes alleged to have taken place in Montgomery between May and November of this year. Federal law prohibits possession of machine guns, including possession of a conversion device. Convictions carry a penalty of up to 10 years in and a $250,000 fine.

Montgomery Police Chief Darryl Albert said the police department has seized 80 machine gun conversion devices since it began focusing on the weapons in March.

Officials said the cooperation between local, state, and federal law enforcement is an important part of the effort to crack down on the devices. The cases announced Friday are part of a collaborative effort called Project Safe Neighborhoods.

The Montgomery Police Department and the ATF investigated the cases announced Friday, with assistance from the U.S. Marshals Service.

FBI Special Agent in Charge Paul Brown and U.S. Marshal Jesse Seroyer also spoke at the news conference about what Ross said is a problem that has grown rapidly.

“This is not something that the office was prosecuting a few years ago,” Ross said. “This is something that the proliferation has been very quick. And I think that does have a lot to do with how easy they are to make and to obtain.”

Officials also showed a small device that can be similarly used to convert semiautomatic rifles, such as AR-15s, to automatic fire.

Those charged are:

• Shykeem Kartarell Grant, 21, possession of a machine gun, felon in possession of a firearm, tampering with a witness by intimidation or threats.
• Quandarius Deandre Lindsey, 30, possession of a machine gun, felon in possession of a firearm.
• Deandre Nyquan Lucas, 20, possession of a machine gun.
• Clarence Anthony McCall, 20, possession of a machine gun, two counts.
• Vandarius Jamal Parks, 21, possession of a machine gun.
• Tavius Smith, possession of a machine gun.
• My’qurious Xavier Solomon, 19, possession of a machine gun, tampering with a witness by intimidation and threats.
• Dequarius Dewayne Thornton, 26, possession of a machine gun, illegal receipt of a firearm by a person under indictment.
• Cammeron Leroy Youngblood, 23, possession of a machine gun, illegal receipt of a firearm by a person under indictment.
• Keonte Martin, 20, possession of a machine gun.
• Jaxon Smith, 19, possession of a machine gun.

Trials for Martin and Jaxon Smith, who were indicted in October, are scheduled for January 8. Trials for the others, who were all indicted Nov. 29, will be scheduled early next year.