n korea plant activity hancocks pkg_00001416.jpg
n korea plant activity hancocks pkg_00001416.jpg
Now playing
01:15
Suspicious activity at North Korea nuclear complex
Nicolas Asfouri/Pool/Getty Images/AFP PHOTO/KCNA VIA KNS
Now playing
01:27
North, South Korean leaders to meet again
Airbus Defense and Space
Now playing
01:44
New images show N. Korea dismantling test site
CNNI
Now playing
00:40
Pompeo dismisses N. Korea's 'gangster' comments
SINGAPORE - JUNE 12: In this handout photo, North Korean leader Kim Jong-un shakes hands with U.S. President Donald Trump during their historic U.S.-DPRK summit at the Capella Hotel on Sentosa island on June 12, 2018 in Singapore. U.S. President Trump and North Korean leader Kim Jong-un held the historic meeting between leaders of both countries on Tuesday morning in Singapore, carrying hopes to end decades of hostility and the threat of North Korea's nuclear program. (Photo by Kevin Lim/THE STRAITS TIMES/Handout/Getty Images)
Handout/Getty Images AsiaPac/Getty Images
SINGAPORE - JUNE 12: In this handout photo, North Korean leader Kim Jong-un shakes hands with U.S. President Donald Trump during their historic U.S.-DPRK summit at the Capella Hotel on Sentosa island on June 12, 2018 in Singapore. U.S. President Trump and North Korean leader Kim Jong-un held the historic meeting between leaders of both countries on Tuesday morning in Singapore, carrying hopes to end decades of hostility and the threat of North Korea's nuclear program. (Photo by Kevin Lim/THE STRAITS TIMES/Handout/Getty Images)
Now playing
01:56
Kim Jong Un snubbed Mike Pompeo, source says
WASHINGTON, DC - MAY 09:  National Security Adviser John Bolton speaks on a morning television show from the grounds of the White House, on May 9, 2018 in Washington, DC. Yesterday President Donald Trump announced that America was withdrawing from the Iran nuclear deal.  (Photo by Mark Wilson/Getty Images)
Mark Wilson/Getty Images
WASHINGTON, DC - MAY 09: National Security Adviser John Bolton speaks on a morning television show from the grounds of the White House, on May 9, 2018 in Washington, DC. Yesterday President Donald Trump announced that America was withdrawing from the Iran nuclear deal. (Photo by Mark Wilson/Getty Images)
Now playing
01:34
Bolton: US has plan for denuclearizing N. Korea
Planet Labs Inc.
Now playing
01:25
Satellite images show missile plant construction
CNN
Now playing
01:14
Susan Rice: Kim Jong Un beat Trump at summit
Images of the Norrth Korea missile launch on November 28 taken from Rodong Sinmun, North Korea's official newspaper.
From Rodong Sinmun
Images of the Norrth Korea missile launch on November 28 taken from Rodong Sinmun, North Korea's official newspaper.
Now playing
02:14
Will North Korea restart nuclear tests?
Photo Illustration/Getty Images
Now playing
03:00
Will Kim Jong Un ever give up his nukes?
Photo Illustration/Getty Images
Now playing
02:27
What's bringing Kim Jong Un to the table
Now playing
01:51
Who is Kim Jong Un?
CNN
Now playing
01:43
Connolly: Trump comment on Kim 'jaw-dropping'
Now playing
02:31
Moon: The masterful dealmaker
Trump Kim Jong Un comment 04240218
CNN
Trump Kim Jong Un comment 04240218
Now playing
01:26
Trump: Kim Jong Un very open and honorable
Now playing
03:06
Finding art on the edge of the DMZ

Story highlights

Monitoring project says it has observed activity at a North Korean nuclear site

Plumes from a smokestack may indicate Pyongyang's nuclear ambitions are advancing

CNN —  

The North Korea monitoring project 38 North says that satellite imagery shows “suspicious activity” at a nuclear enrichment site in North Korea.

Plumes of exhaust steam, a byproduct of heating the main plant at the Yongbyon Radiochemical Laboratory complex, have been seen in commercial satellite images taken March 12 and over the preceding five weeks, the group says.

Trump on potential war between Japan and North Korea: ‘If they do, they do’

This activity is unusual, the report by the Washington-based project says.

“Exhaust plumes have rarely been seen there and none have been observed on any examined imagery this past winter,” the report says.

“The plumes suggest that the operators of the reprocessing facility are heating their buildings, perhaps indicating that some significant activity is being undertaken, or will be in the near future.”

Weeks away?

The plumes of steam do not necessarily indicate that the process for refining plutonium for nuclear weapons is underway or will be soon, the report says.

It does, however, note that U.S. Director of National Intelligence James Clapper recently testified that Pyongyang had “announced its intention to ‘refurbish and restart’ its nuclear facilities,” including the uranium enrichment facility at Yongbyon, and that it could be able to recover plutonium from the reactor’s spent fuel “within a matter of weeks to months.”

Separate images appear to show further work on the site’s Experimental Light Water Reactor, a key facility for the enrichment of nuclear fuel, is ongoing, with a new transformer yard and road built, and the installation of electrical cables completed.

The report states that “slow, steady progress” is being made on the ELWR component of Pyongyang’s nuclear project.

Construction of new buildings near the Uranium Enrichment Complex is also ongoing, with some buildings nearing completion and new projects started. While there is speculation as to the purpose of these new buildings, the report says evidence is insufficient to reach any firm conclusions.

Construction of new facility near the uranium enrichment complex continues.
Airbus Defense & Space/38 North
Construction of new facility near the uranium enrichment complex continues.

Evidence of activity at the plant’s smaller 5 MWe reactor has also been observed, but this part of the facility does not appear to be operational as exhaust steam from the cooling tower has not been noted.

Vehicle activity can be seen around the 5 MWe reactor.
Airbus Defense & Space/38 North
Vehicle activity can be seen around the 5 MWe reactor.

How North Korea’s nuclear program went from threats to reality

South Korea monitoring

South Korean officials said they were aware of the report. “We are looking into … and closely monitoring the situation,” South Korean Defense Ministry spokesman Moon Sang-gyun said during a regular news conference Tuesday.

Earlier in 2016 the think tank reported “slow progress” at the ELWR.

In January, North Korea announced what it said was a successful test of a hydrogen weapon, and more recently it claimed that it had miniaturized warheads.

This is North Korea’s nuclear timeline

In recent months it has also fired a number of missiles, along with the launch of what it said was a satellite, but which many observers believe could be used as an intercontinental ballistic missile.

Two U.S. defense officials said the United States has observed movement recently of mobile intermediate-range missile launchers. Even though there are no missiles on the launchers, there is concern North Korea could have a launch planned, the officials said.

These launchers could hold a Musudan or KN-08, the missiles that worry the United States the most, the officials said. North Korea is said to be working on an upgrade though it hasn’t even formally tested these missiles.

There is limited activity at the ICBM launch site, but no indication of a launch, they said.

CNN’s Barbara Starr contributed to this report.