Seoul, Jan 25 (IANS): South Korea has not detected any signs of North Korea trying to restore underground tunnels at its purportedly demolished Punggye-ri nuclear test site despite indications of maintenance work there, a Seoul official said on Tuesday.

The official's assessment came after Olli Heinonen, a former deputy director-general at the International Atomic Energy Agency, told the Voice of America (VOA) that the North is maintaining the site as evidenced by "trails of the cars and cleaning of snow", reports Yonhap News Agency.

In May 2018, the North claimed to have demolished the site in a show of willingness to denuclearise. The following month, it committed to work toward the "complete denuclearization" of the Korean Peninsula at the first-ever summit with the US in Singapore.

"We have identified the reported maintenance activities at part of the facilities there, but we have not detected any signs of activities to restore tunnels," the official told reporters.

Commenting on the VOA report, the Joint Chiefs of Staff (JCS) said that the intelligence authorities of South Korea and the US are keeping close tabs on North Korean activities at the site.

"Since the closure of the nuclear testing site in Punggye-ri, we have been paying close attention to related activities there," a JCS official told reporters. "To date, there is no noteworthy change."

In the VOA report, Heinonen cited two possible reasons for the North's activities to maintain the site, including the monitoring of any release of radioactivity from it.

The signs of activities at the Punggye-ri site came after Pyongyang issued an apparent threat to discard its self-imposed moratorium on nuclear and long-range missile tests amid a protracted impasse in nuclear negotiations with Washington.