A US delegation returned to South Korea Saturday with some 18,000 pages of documents from Pyongyang detailing North Korea's nuclear activities over more than 20 years, reported dpa.
The documents, which describe the operations of three facilities at the communist nation's nuclear complex in Yongbyon, would be brought back to the United States to be evaluated, said delegation leader Sung Kim, director of the State Department's Office of Korean Affairs, after crossing the heavily-guarded border between North and South Korea.
The State Department in a statement said the documents consist of operating records for a five-megawatt nuclear reactor, a fuel reprocessing plant and fuel fabrication facility at Yongbyon, going all the way back to 1986.
While the pages were yet to be "examined thoroughly," they were expected to cover three separate efforts over the years by the North Koreans to reprocess plutonium.
The Yongbyon complex was shut down and sealed in July 2007 as part of a six-party agreement earlier in the year, under which North Korea should eventually dismantle its nuclear weapons programme entirely.
The State Department said eight out of 11 disablement activities at the complex had been completed and verified by US experts on the ground.
The disablement, along with the verified discharge of about one- third of the country's spent fuel rods, meant North Korea was no longer able to produce weapons-grade plutonium for its nuclear programme, the US said.
The US has been pushing North Korea to make a full declaration of its nuclear activities, including its possible ties to an alleged Syrian nuclear programme that the US last month said North Korea had helped create. Both North Korea and Syria have denied the charges.
The 18,000 documents handed over by North Korea on Thursday were an "important first step in the process of verifying that North Korea's declaration is complete and correct," the State Department said.
The six-nation talks, aimed at denuclearizing the Korean Peninsula, involve the two Koreas, the United States, China, Japan and Russia.