According to a new study, satellite images from June 21 has shown that North Korea is upgrading the infrastructure at its only nuclear research facility used to fuel its weapon programs — the Yongbyon Nuclear Scientific Research Center — despite its pledge to denuclearize and the agreement with U.S. President Donald Trump.

The upgrades include construction of a new cooling water pump and new buildings. The reactor’s cooling system has already been modified, according to a report by a prominent North Korea monitoring group. Also, a small non-industrial building of an unknown purpose was erected at the radiochemical laboratory.

The report states that the staining at the northwest corner of the cascade halls caused by the deposition of water vapor from the six cooling units at the facility shows that the uranium enrichment plant is operational. The necessary infrastructure for the reactor to operate looks externally complete but there is no proof to suggest that the operations have begun, it added.

“Although a small water discharge is visible from the cooling water outfall pipe going into the river, that discharge is less than has been observed previously when the reactor was fully operational,” the report said.

However, experts have warned that work at the nuclear reactor should not be seen as having any relationship to North Korea’s pledge to denuclearize.

“The North’s nuclear cadre can be expected to proceed with business as usual until specific orders are issued from Pyongyang,” the experts said, The Guardian reported.

North Korean leader Kim Jong Un had earlier pledged to denuclearize the Korean peninsula but the details of how and when that will happen have not been decided yet. He also said North Korea closed it’s only known nuclear test site in May.

In May, Han Tae Song, North Korea’s ambassador to the United Nations, said, "The discontinuation of nuclear tests is an important process for global disarmament, and the DPRK will join the international desire and efforts for a total halt of nuclear tests."

In the same month, two dozen handpicked foreign journalists from Britain, China, South Korea, Russia and the United States were called to witness the dismantling of the Punggye-Ri Nuclear Site, where the nation conducted its all six nuclear tests. There were four tunnels at the site but journalists saw the destruction of only three on them at the time. Officials later said that the fourth tunnel was already closed down.

However, experts said that dismantling the nuclear site is equal to destroying the evidence.

"If I were going I would want to bring some capability of taking samples, and I would also want to bring a geologist with me. I'd want to have a radiation counter, I would want to go into the tunnel to see if parts of it have caved in the back, and I would want to take radiation measurements,” said Cheryl Rofer, a chemist who spent 35 years working on environmental cleanups.