WASHINGTON (Reuters) - The underground nuclear test site that North Korea has pledged to dismantle remains usable in spite of damage from a previous blast, and its closure could easily be reversed, U.S. intelligence officials said on Friday.

“There is no reason to conclude that the Punggye-ri test site is no longer functional,” said one U.S. intelligence official, speaking on condition of anonymity because of the sensitivity of the issue.

The U.S. intelligence officials’ comments appear to contradict recent academic reports that suggested the range was rendered possibly unusable by a September nuclear test.

Pyongyang pledged in the run-up to Friday’s historic summit between North Korean leader Kim Jong Un and South Korean President Moon Jae-in that it would dismantle Punggye-ri to “transparently guarantee” a pledge to discontinue nuclear and ballistic missile tests.

The Kim-Moon summit was held in advance of a meeting Kim is expected to have in late May or early June with U.S. President Donald Trump, who is demanding that the North Korean leader verifiably eliminate his nuclear weapons program.

North Korea has conducted all six of its nuclear tests at Punggye-ri, which consists of tunnel networks burrowed beneath Mount Mantap in the country’s northeast.

A detonation last September of what North Korea said was a successful hydrogen bomb test was found by recent academic reports to have been so large that it triggered a collapse inside the mountain, rendering the entire site geologically unusable for future tests.

The U.S. intelligence officials said that Punggye-ri remains usable, despite what a second official called “some minor geological disturbances” around Mount Mantap that could be natural or triggered by the September test.

Even if one test tunnel collapsed, others within the complex still can be used, said the first official.

Jeffrey Lewis, the director of the East Asia Nonproliferation Program at the Middlebury Institute of International Studies, said that commercial satellite images showed activity at a test range location known as the “western portal” as recently as the middle of this month.

North Korea’s pledge to dismantle the range is largely symbolic because at most that would involve sealing test tunnels with concrete that could easily be removed if Kim decided to restart underground blasts.

“It’s nicer of him than saying ‘I’m going to continue testing.’ But they are just tunnels in the mountain. You can seal them, but you can just open them back up,” Lewis said.

The second U.S. official concurred, saying that Punggye-ri could be reactivated “in a relatively short period of time” if it is closed.

If Pyongyang does halt nuclear testing and shuts the site, the second official said, “It will be possible to ascertain with existing monitoring whether it is being put out of commission permanently or merely closed.”