U.S. envoy Bill Richardson (search) toured a North Korean nuclear facility Wednesday and held a second day of talks with government officials as part of his efforts to encourage Pyongyang to dismantle its atomic weapons program.

The Democratic governor of New Mexico spent about two hours at North Korea's main nuclear research facility at Yongbyon, where the communist regime is known to have secretly processed plutonium for nuclear weapons, Richardson's chief of staff Billy Sparks told the Associated Press in a phone call from Pyongyang.

Sparks also said Richardson met with officials but provided no details.

Richardson, a former U.S. ambassador to the United Nations (search), said before his trip that he would push the North Koreans for specifics on how they plan to dismantle their weapons program and a commitment to allow outside verification of the process.

He also said he will urge Northern officials to cooperate with humanitarian aid organizations and allow them to operate more freely in the country.

The governor, who has been to North Korea (search) several times before, was invited by the North Koreans in May but postponed his trip when Washington asked him to wait until the completion of the latest round of nuclear talks in Beijing.

The talks ended last month with North Korea committing to abandon its nuclear program, which Pyongyang claims has already yielded a weapon. The next round of talks, which also involve China, Japan, South Korea and Russia, was scheduled for November but no date has been set.

Richardson was accompanied by public health, energy and other officials from New Mexico; he said earlier he hopes their presence would show the North Koreans what kind of assistance they could expect in return for giving up nuclear weapons.

The entourage arrived in North Korea Monday evening and was to stay until Thursday, travel next to Japan and South Korea (search) to brief officials before returning to New Mexico on Oct. 22.