North Korea has started operating a new nuclear facility that could boost its production of uranium-enriched fuel for nuclear weapons, Joongang Ilbo newspaper reported Wednesday, citing a South Korean official. The new plant is reportedly located within the Yongbyon nuclear power plant, which houses the country’s sole plutonium-producing nuclear reactor.

The South Korean news report stated that infrared cameras with heat sensors used by South Korean and U.S intelligence agencies had detected the operation of centrifuges inside the plant. The report revealed that the new plant was built next to a uranium facility -- with about 2,000 gas centrifuges -- which was shown to a team of U.S. nuclear experts in 2010.

“We have to monitor a little longer to see if the new plant actually started producing weapons-grade materials, but it is our assessment that it is in operation,” a South Korean official in charge of North Korean intelligence said, according to Joongang Ilbo. The official added that the new plant is of the same size as the old one and could have the same number of gas centrifuges.

“If the North operates all 4,000 centrifuges year-round, it can produce about 80 kilograms (176 pounds) of highly enriched uranium annually,” a nuclear engineer from a state-run institute told Joongang Ilbo. “That is enough to build four to five nuclear bombs.”

However, a defense ministry official declined to comment on "any matters of intelligence," according to Agence France-Presse.

In 2013, North Korea had reportedly threatened to restart all its facilities at Yongbyon after its third nuclear test failed in February.

Earlier this year, a U.S. intelligence official had said that the North may have taken steps to boost its ability to build nuclear weapons by expanding a uranium-enrichment facility, The Wall Street Journal reported at the time.

A top U.S. official responsible for handling North Korea’s nuclear issue reportedly said in October that efforts are being made to convince Pyongyang that only denuclearization could bring security and prosperity to the reclusive, poverty-ridden nation.

“North Korea must demonstrate that it is serious about denuclearization. We need to be certain that is prepared to live up to its international obligations and abide by international norms of behavior,” U.S. Secretary of State John Kerry had said in October.