An American official has said it looks like North Korea has handed over all the documents it has on plutonium production.
Sung Kim is U.S. Office Director of Korean Affairs at State Department Sung Kim.
"I do think these documents are an important first step in terms of verifying North Korea's declaration. On a very, quick preliminary view, it does appear that they are complete; daily logs, operational logs, books, operational records, operation records of receipts, operational records of co-extraction process, so they appear to be a complete set."
Sung Kim has traveled to North Korea to pick up the documents in seven large boxes and returned to Washington on Monday.
He said a full review by an inter-agency team from the departments of State, Energy and intelligence organization would take several weeks.
Kim said it was too early to say when the complete record would be provided, but he sounded optimistic that North Korea was working on it.
"Obviously, the documents themselves are alone not enough. We will need to conduct a very full verification, including access to their facilities, sampling, interviews with personnel involved in the programmes, but these documents are an important first step."
Under an agreement last year with South Korea, the United States, China, Japan and Russia, the current phase of denuclearisation obliges North Korea to declare and disable all its nuclear programmes in exchange for U.S. food aid.
It is to be followed by the third and final phase in which Pyongyang must give up all its fissile material.
In related development, the United States has said it's working on a new proposal to send emergency food aid to North Korea.