In an effort to combat “ghost guns” in Pennsylvania, state authorities on Monday said they had advised the State Police that the partially assembled guns known as “80% receivers” should be treated as firearms.

At a news conference in Harrisburg, Attorney General Josh Shapiro, standing with Gov. Tom Wolf, said he issued a legal opinion Monday to the State Police to clarify that 80% receivers should be considered firearms when it comes to enforcing state laws on illegal firearms possession.

“My office is taking the initial step of clarifying — through my official, legal opinion — that under Pennsylvania law, 80% receivers are firearms and can be treated, regulated, and enforced as such,” Shapiro said during the news conference, held in the Governor’s Reception Room at the state Capitol and live-streamed online. “The proliferation of these untraceable weapons strikes at the heart of our public safety, hindering law enforcement’s ability to protect our communities. Today we take the first step in addressing this problem.”

Ghost guns are homemade, 3D-printed, or partially assembled firearms sold with the parts needed to create a fully operational gun. They don’t have serial numbers and thus are untraceable by law enforcement.

A receiver, or frame, is the part of the firearm that houses the internal firing components. A gun cannot function without a receiver. In essence, an “80% receiver” is the frame or skeleton of a gun that is in an incomplete stage of manufacture, but can easily be turned into a functioning firearm.

“We’re here today because too many moms have buried their children,” Shapiro said, mentioning Kensington. “We’re here today because too many ... neighborhoods continue to be wracked by excessive gun violence. We’re here today because too many criminals have taken advantage of loopholes to gain access to guns that they should never have been able to in the first place.

“With my legal interpretation today, we can ... save lives,” Shapiro said.

In Philadelphia, Shapiro said, “we’ve seized 100 of these ghost guns ... this year and they’re increasing as the months go on."

Wolf said at the news conference that he was adding his support “to classify these 80% receivers as a firearm.”

“If something is manufactured to expel a projectile by an explosive, it’s a firearm — whether it needs a few holes drilled in it or some assembly,” Wolf said.

Before Monday, Shapiro said, “if we came upon a felon who was not permitted to purchase a gun and we found one of these [receiver] kits on their person, it would not have been illegal" for them to have the kit. "Now as a result of our legal opinion and them being a felon not to possess, these will be treated as firearms.”

The Pennsylvania State Police, which also participated in Monday’s news conference, will convey the new legal interpretation about the 80% receivers to gun shop owners and vendors, and directors of gun shows, Shapiro said.

He noted that 80% receiver kits are not illegal by themselves.

“Neither the State Police, the governor, or I want to infringe on the legal rights of anyone to purchase 80% receivers,” Shapiro said. “We want to stop people who are not permitted under the laws of this commonwealth to own a gun from being able to get their hands on one.”

New Jersey has already taken criminal and civil action against “ghost guns.”

Last year, Gov. Phil Murphy signed into law legislation that made it illegal to purchase parts to manufacture or distribute information to print ghost guns.

In March, New Jersey Attorney General Gurbir S. Grewal filed the state’s first lawsuit against a “ghost gun” company, California-based U.S. Patriot Armory, which authorities said sold an assault firearms kit online to an undercover state investigator. The lawsuit alleged that James Tromblee Jr., the company’s founder and owner, violated the state’s Consumer Fraud Act by continuing to advertise and market ghost guns to New Jersey residents, and by delivering the assault firearms kit to the New Jersey buyer.

Earlier that week, Grewal announced the arrests of and criminal charges against 12 men who authorities said were part of a Camden County criminal network that trafficked untraceable, build-it-yourself AR-15 assault rifles.