SEOUL — Human rights groups and defector organizations have spent weeks now investigating rumors about the closure of Camp 22, North Korea’s largest political prison camp, and the only thing proven so far is the North’s expertise at keeping secrets.

The Daily NK, an online newspaper in Seoul staffed largely by defectors, has run several recent stories — attributed to anonymous sources — saying the gulag was closed earlier this year. But the Committee for Human Rights in North Korea (HRNK), after studying the latest satellite photos of the camp, said the camp still seems to be operating, with fields well-tended and coal piled near loading facilities.

Of course even these conflicting reports give little hard evidence of what’s going on at the camp in the country’s frigid northeastern corner. If indeed prisoners were relocated from Camp 22, there’s no leading theory for why. (The Daily NK suggested that the prison was shuttered because the state wanted to “cover its tracks” after a warden fled to China; some analysts, though, dismiss that idea, saying the camp can easily carry on with its regular brutality even after the minor breach.) It’s also possible that regular citizens, rather than prisoners, are now using the camp.

HRNK Executive Director Greg Scarlatoiu speculated in an e-mail that North Korean authorities might be “in the process of turning the camp into a ‘Potemkin Village,’ ” so years down the road “they can just invite international inspectors to the area, just to prove that it has always been the picturesque village they've always claimed it was.”

North Korea is often described by outsiders as the world’s most secretive state, and its political prison camps — known within the country as Total Control Zones — are kept under more layers of secrecy than almost anything else. The authoritarian police state has never acknowledged that the camps exist. Foreign visitors do not see the camps and few prisoners escape. To date, no former prisoner from Camp 22 has ever reached South Korea, according to a comprehensive 2012 report on the camps from the Seoul-based Database Center for North Korean Human Rights.

Today Pyongyang operates six giant political prison camps as well as dozens of smaller facilities that emphasize “re-education” as well as pure labor. At all but one of those major gulags, prisoners stay for life and remain officially "missing" even after they die. Amnesty International estimates that the North holds roughly 200,000 people at these gulags — one in every 120 citizens.

The camps, and the threat of being sent there, underpin the system of fear and punishment that the ruling Kim family has used for decades to hold power and eliminate opponents. Few believe the potential closure of Camp 22 indicates a change in that system. A closure, instead, would be based on more pragmatic calculations: The North has previously relocated prisoners, for instance, when seams at coal mines dried up — meaning the camp lost its usefulness to the country’s decrepit economy.

If anybody has insight into how and why North Korea closes a prison camp, it’s a defector named Ahn Myong-chol. During his late teens and early 20s, Ahn worked as a North Korean prison guard at several camps, including two that were closed down while he was in the North — Nos. 11 and 13. Ahn then moved on to camp No. 22, where he worked for four years before defecting in 1994. Along with a former employee of the North’s security agency, Ahn is just one of two people to provide public testimony about Camp. 22.

He works now at the northern tip of a country road in South Korea, past rows of squid and dried fish restaurants, in an observation tower overlooking the demilitarized zone, and I went to visit him late last week. Most days, Ahn gives tours to visiting school groups. They drink soda from vending machines and giggle because they’re on a field trip. Ahn often doesn’t tell them he’s from the North.

But he remains fascinated about the gulag where he used to work. He spoke last week with a friend who lives just outside the Camp 22 gates, he said, and the friend told him that former guards were coming into town to sell off goods and produce — oil, corn and meat. The friend also said that “regular people” now go into the camp and farm or mine.

“I suspect the camp was closed because it’s running out of coal,” Ahn said. “There’s a limit to how much you can dig out. Even when I was there in 1994, people were saying Camp 22 would run out of coal to mine in five years.”

The camp exists almost entirely to take advantage of its unpaid, poorly fed and easily replaceable workforce. About 30,000 of the camp’s 50,000 prisoners work in the mines, Ahn said, and they do all the digging manually. Major injuries are commonplace, he said. So are deaths. When an underground fire broke out during Ahn’s time at the camp, some workers were asked to use explosives to create an intentional cave-in. That prevented the fire from spreading. But it also trapped 1,000 prisoners who were on the wrong side of the explosion, Ahn said.

“They burned,” he said.

Before I left, I asked Ahn about how North Korea closes a camp.

In both cases he was familiar with, he said, most of the camp was left standing. Authorities took down guard towers and dynamited military-related facilities and torture rooms. But harvesting continued (sometimes with regular citizens) at least through the fall season. 

I handed Ahn the satellite images obtained by HRNK, and he took them home to analyze them.

By the next morning, Ahn arrived at a different conclusion than the NGO. He said the images proved the camp’s closure. The changes between photos from October 2012 and May 2011 were minor, but critical.

“The detention center is gone and two interrogation facilities are gone,” Ahn wrote in an e-mail. “[The] guard building has disappeared as well. I couldn't check if the guard posts along the fences are gone because the photo didn't cover that part, but based on the findings I think Camp 22 is no longer operating as a prison.”

Ahn added, "I feel sorry to find out the prison is closed because it doesn't mean the prisoners are liberated. They're moving to a different location and probably will have to go through more severe hardship."

Yoonjung Seo contributed to this report.