As the technology to print 3-D firearms advances, a federal law that banned the undetectable guns is about to expire.

U.S. Sen. Chuck Schumer said he’s seeking an extension of the law before it expires Dec. 9.

He said the technology of so-called 3-D printing has advanced to the point anyone with $1,000 and an Internet connection can access the plastic parts that can be fitted into a gun. Those firearms can’t be detected by metal detectors or X-ray machines.

Schumer said that means anyone can download a gun cheaply, then take the weapons anywhere, including high-security areas.

The Democrat is pushing the extension along with Sens. Patrick Leahy of Vermont and Bill Nelson of Florida. The effort was announced Sunday.

Agents from the Bureau of Alcohol, Tobacco, Firearms and Explosives 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 so that the firearm is detectable by scanners at airports, federal buildings, sporting events — any place where security screening is in place. If the law expires, someone could legally make and sell firearms that are undetectable.

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 3-D printing technology has recently advanced to create handguns capable of shooting several shots, rather than just one, before it ceases to function.

A blueprint for one such firearm was recently downloaded more than 100,000 times, Schumer said.

“We are looking at a world in which anyone with a little bit of cash can bring an undetectable gun that can fire multiple bullets anywhere — including planes, government buildings, sporting events and schools,” Schumer said. “3-D printers are a miraculous technology that have the potential to revolutionize manufacturing, but we need to make sure they are not being used to make deadly, undetectable weapons. “