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Calling 3-D plastic guns an “extremely serious problem,” Attorney General Eric Holder called on Congress to renew a law that requires all firearms to be subject to metal detection.

The Undetectable Firearms Act, a law first enacted in 1988 and then reauthorized in 2003, makes it illegal to “manufacture, import, sell, ship, deliver, possess, transfer or receive” any firearm that’s undetectable by scanners. But the law is set to expire Dec. 9, unless Congress again reauthorizes it. Holder said the new technology of printing 3-D guns made of plastic means guns could potentially be smuggled onto planes, into federal buildings or at large public events.

“This is an extremely serious problem,” Holder said in a statement. “This is a very worrisome threat to law enforcement and to people who fly every day. We can’t have guns legally in circulation that are not detectable by metal detectors.”

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Two Democratic senators, Chuck Schumer of New York and Bill Nelson of Florida, have called for a ban on plastic guns. Rep. Steve Israel, D-N.Y., has also introduced legislation on the issue.

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"The expiration of this law, combined with advances in 3-D printing, make what was once a hypothetical threat into a terrifying reality," said Schumer. "We are actively exploring all options to pass legislation that will eliminate the problem."

Regardless of personal feelings on gun control legislation, Holder said the act should “needs to be reauthorized” and even expanded.

“I would think that this should enjoy broad, bipartisan support and could be done swiftly and quickly,” Holder’s statement continued. “That is what we will be pushing for.”

In a meeting with reporters Wednesday, agents from the Bureau of Alcohol, Tobacco, Firearms and Explosives said plastic guns present a special challenge for law enforcement agencies.

The agents said that in order to comply with current law, a person manufacturing a gun must use a certain amount of metal in the finished product – 3.7 ounces -- so that the firearm is detectable. A loophole in the existing law allows someone to make an illegal gun legal by simply attaching a removable metal piece to the weapon. That piece could be removed if someone wanted to sneak the weapon into a protected location.

The Wall Street Journal reported earlier this week that ATF agents said there are not any known instances of a person being shot with a plastic gun in the U.S., nor are there any open criminal investigations involving one.

Additionally, officials do not believe there’s a risk that street criminals will be able to mass produce guns using 3-D printing technology, as the printer required to produce a gun can cost more than $100,000 and quality varies.

"This is more for someone who wants to get into an area and perhaps be an assassin," Richard Marianos, an official with the Bureau of Alcohol, Tobacco, Firearms and Explosives, told the Wall Street Journal. "Or they want to go to a courthouse and shoot a witness."