A South Korean media report said authorities in Washington and Seoul have not found concrete evidence yet that North Korea has restarted a plant used to make nuclear weapons.
According to a report Wednesday from South Korea's Yonhap news agency, U.S. satellite pictures show activity at North Korea's main Yongbyon nuclear complex.
But an anonymous official quoted in the report said a krypton detector has not shown any signs the North has started reprocessing at the plant. Krypton gas is released when spent fuel rods are reprocessed.
The report said sensors for the gas are deployed near the border with the North.
Last month, North Korea threatened to restart reprocessing work at its once closed Yongbyon nuclear complex. The move was a retaliation to international criticism of its April launch of a rocket it says was fired to put a satellite into space.
The United States and other countries believe the rocket was a test launch for a ballistic missile.
In addition to threatening to restart its Yongbyon facility, North Korea has also dropped out of six-party talks aimed at ending its nuclear weapons programs and said it will conduct nuclear and ballistic missile tests.
Washington's top nuclear envoy, Stephen Bosworth, returned from a trip to the region earlier this week that included stops in China, Japan and South Korea.
Bosworth said Washington is ready for direct talks with Pyongyang. North Korea has yet to respond to the offer.
Some information for this report was provided by AFP and AP.
