Pakistan has said a probe into possible nuclear technology transfers to Iran has shown some of its scientists may have been "motivated by greed".
Pakistan says it takes its nuclear responsibility very seriously
Pakistan launched the investigation following information from Iran and the International Atomic Energy Agency.
Foreign Ministry spokesman Masood Khan said: "There are indications certain individuals might have been motivated by personal ambition or greed."
Mr Khan insisted that the government had never authorised any transfer.
He said Pakistan would investigate the matter fully and take legal action against anyone involved - if the allegations were true.
But he stressed that the probe had not yet made a "final determination".
"Let's not jump to any conclusions," he told a news conference in the capital, Islamabad.
No state institution had ever transferred nuclear technology, Mr Khan said, and never would.
But insiders like the former head of the Pakistani intelligence service, Hamid Gul, say it would be impossible for eminent nuclear scientists to mount freelance operations undetected.
He told the BBC comprehensive security and profiling arrangements follow them through their working lives and beyond into retirement.
Mr Khan said that only a "very small number" of Pakistan's scientists were being questioned.
"We had been approached by the IAEA [International Atomic Energy Agency]. We had been given some information by the government of Iran. The information that was shared with us pointed to certain individuals and we had to hold the debriefing sessions," he said.
Abdul Qadeer Khan - questioned, but not being detained
On Monday, the government said the father of Pakistan's nuclear weapons programme, Abdul Qadeer Khan, was
At least two scientists from the country's top nuclear facility, Khan Research Laboratories, were also debriefed this month.
One of them is former director-general Mohammad Farooq, who is still being held.
Pakistan has always denied helping states such as Iran and North Korea with their nuclear programmes, saying it takes its responsibilities as a nuclear state very seriously.
However, allegations that nuclear skills and know-how have been transferred to countries dubbed "rogue states" by Washington refuse to go away.
Last weekend, reports in the New York Times and the Washington Post fuelled speculation that Pakistan may have provided Iran and North Korea with crucial technology to enrich uranium for nuclear weapons use.
On Monday, Washington said Pakistani President Pervez Musharraf had assured it that Islamabad had not "in the present time" provided nuclear secrets to such countries.
White House spokesman Scott McClellan said the US and Pakistan would continue to work closely to fight terrorism despite possible past transfers of technology.