It has been revealed that a few of the six South Koreans released by North Korea last Friday had a history of posting pro-North Korea propaganda on the Internet before they traveled to the North.
Authorities investigating the case said that the six detainees went to North Korea between 2009 and 2012, crossing the Yalu or Tumen River, which are both near the border between North Korea and China.
Authorities say that family issues and business failures may have prompted some of them to post messages that praised North Korea, Arirang News reports.
They said that the individuals were also under the impression that they would be treated well upon arrival in North Korea, but they were instead detained for years and interrogated.
The six were returned on Friday at the border village of Panmunjom, according to The New York Times.
The identities of the detainees have not been released. The ministry said they are South Korean men between the ages of 27 and 67.
In February 2010, Pyongyang said that it was holding four South Koreans for illegal entry, but did not respond to Seoul's request to have them identified and released. This June, the North said it was holding "several" South Koreans for illegal entry, but did not give any details about the detainees.
Thousands of South Koreans, mostly fishermen, have been taken and detained in the North in the years since the Korean War. More than 500 of these men have not returned, although Pyongyang denies holding them against their will.
The Unification Ministry of South Korea welcomed the news on Thursday. "Although it is belated, we consider it a good thing that the North has decided to take this humanitarian measure," the Ministry said. "We will get custody of our six citizens, verify their identities and find out how and why they entered the North."
North Korea has been sending conflicting messages in recent weeks, some conciliatory, and others less civil. In mid-September, South Korean vehicles crossed into the North to work on a jointly run industrial park in the North Korean border town of Kaesong. The complex has been abandoned since April when North Korea withdrew its workers after tensions arose due to the North's most recent nuclear test.
But after the complex opened, North Korea postponed the resumption of a humanitarian program in which families divided by the Korean War could hold reunions. The North postponed the program because of what they called the "reckless and vicious confrontational racket" of the conservative government of Park Geun-hye, the South Korean president.
This month, North Korea told Ms. Park to "watch her mouth" and threatened to "rain fire" on the South after South Korean leaders said the North's maintenance of its nuclear arms program would not be possible while also attempting to revamp the economy. The North also put is military on high alert this month and warned the U.S. of "disastrous consequences" for moving warships into a South Korean port for a military exercise.
Yet, North Korea is allowing South Korean officials to visit the Kaesong complex next week. North Korea wants to expand the complex, where low-paid workers make labor-intensive goods such as shoes and textiles. North Korean leader Kim Jong-un aims to use the complex to attract more foreign investment and improve living standards for North Koreans.
However, the South is skeptical of expanding the project due to the prospect of another shutdown.