North Korea on Monday invited every member of the U.S. Congress to inspect the Pyongyang Bio-Technical Institute.

“Come here right now, with all the 535 members of the House of Representatives and the Senate as well as the imbecile secretaries and deputy secretaries of the government who have made their voices hoarse screaming for new sanctions,” said a spokesman of the North’s National Defense Commission, according to the official Korean Central News Agency.

North Korean leader Kim Jong Un had recently toured the Institute himself; state-run media released photographs of the visit last month. Officially, the facility makes pesticides for farming. But the pictures—as the Center for Nonproliferation Studies’ Melissa Hanman noted in a damning and recently-released report—suggest something far more sinister: a government-run bioweapons factory. In releasing the images, it is possible the regime intentionally disclosed its ability to make anthrax.

Hanman, writing on the website of Johns Hopkins University’s U.S.-Korea Institute, stated that the photographs from the tour indicate the North had illicitly procured equipment and ingredients. For instance, an image showed fermenters, which are listed by the 42-nation Australia Group as controlled items that may not be sold to North Korea.

There was also a PH-Series incubator made in China. Beijing, although not a member of the Australia Group, maintains similar controls, including a “catch all” provision banning the sale of items that exporters think might be used to produce weapons of mass destruction.

Moreover, a photograph showed bottles that look like they came from American companies Merck and Sigma-Aldrich. It appears these items were exported to North Korea in violation of U.S. prohibitions on the sale of pharmaceuticals to the Kim regime.

If the photos do indeed reveal these off-limits equipment and ingredients, then the North has been successful in evading sanctions.

Hanman perceptively asked why North Korea would have gone to the trouble of acquiring contraband equipment when it could have bought all the fertilizer it required on the open market for far less. The answer is chilling: Pyongyang wanted the ability to produce “military-sized batches of biological weapons, specifically anthrax.”

Ostensibly, the equipment was all acquired to grow Bacillus thuringiensis for natural pesticides. But that gear can be sterilized and then used to make Bacillus anthracis. “The bottom line,” she writes, “is that regardless of whether the equipment is being used to produce anthrax today, it could in the near future.”

In fact, most analysts believe the North had weaponized anthrax long ago. In 2009, for instance, the International Crisis Group issued a widely cited report that included information on Pyongyang’s anthrax weapons.

It is not a good sign that, although North Korea is a signatory to the Biological and Toxin Weapons Convention and so has agreed not to develop, produce, or use biological weapons, the Institute that supposedly makes fertilizer is run by Korean People’s Army Unit 810.

North Korea released the photographs on the heels of the revelations that the U.S. had accidently shipped live anthrax to Osan Air Base in South Korea. Pyongyang has interpreted the development not as a horrible mistake but as an ominous threat. Two days before the release of the pictures, the regime accused the U.S. of “biological warfare schemes.”

Of course the North Koreans could have inadvertently revealed their anthrax-making capabilities—they are as capable of incompetence are we are—but it is more likely they wanted analysts like Hanman to study the pictures as a way of reminding Seoul and Washington that they too had stores of deadly germs.

North Korea not only has anthrax and other biological agents on tap, it has almost certainly tested them on its own citizens, especially the deformed and disabled. Im Cheon Yong, a former special operations officer who defected in the 1990s, said he first witnessed a test involving anthrax and chemical weapons in 1984. “For the biological and chemical warfare tests, we needed ‘objects.’” he said. “We watched the instructors carrying out the test on humans to show us how a person dies. I saw it with my own eyes.”

There have been eyewitness accounts more detailed and gruesome than this. But are they true? “We have had credible witness testimony that human experimentation has occurred, especially on the disabled, but we do not have substantiation yet,” Greg Scarlatoiu, executive director of the Committee for Human Rights in North Korea, told The Daily Beast on Tuesday. Military analyst Joe Bermudez notes there probably has been “low-level lethal testing of chemical agents on unwilling human subjects” for some time.

Many hope we will see a smoking gun soon. On the same day the regime showed off the Pyongyang Bio-Technical Institute, a 47-year-old scientist known only as Mr. Lee fled his North Korean research center near the Chinese border. He successfully left the country and ended up defecting to Finland. He claims to have carried with him a 15GB storage device with evidence that the Kim regime tested biological weapons on humans. Activist groups are arranging for Lee to present his evidence to the European Parliament soon, but not everyone is convinced that this defector is the one to finally offer proof. As Scarlatoiu said of Lee, “I’m skeptical.”

At the same time, the Security Council is considering referring North Korea to the International Criminal Court for crimes against humanity. That phrase is vague, but testing weapons of mass destruction on humans should qualify. If the Security Council does not vote to send Pyongyang to The Hague—China is blocking the referral—the phrase will have lost all meaning. If Lee, the defector, or someone else can substantiate the human-experimentation claims, North Korea must pay some price for conducting Mengele-like experiments over the course of decades.

The European Parliament—and the rest of the world—await the testimony of Mr. Lee. In the meantime, North Korea has just demonstrated that in a military-run facility it has developed the capability to mass-produce anthrax.

Gordon G. Chang is the author of Nuclear Showdown: North Korea Takes On the World. Follow him on Twitter @GordonGChang.