Acknowledging that "certain individuals" might have been motivated by "personal greed" to share nuclear technology with Iran, Pakistan on Tuesday said it is questioning several scientists, including father of its nuclear bomb Dr A Q Khan, in this regard.

The probe was set off by a spate of reports in the international media that Pakistan may have contributed to the nuclear programmes of Iran, North Korea and Libya.

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"There are indications that certain individuals might have been motivated by personal ambition or greed, but...we have not made a final determination," Pakistan Foreign Office spokesman Masood Khan told reporters in Islamabad. He admitted that investigations had been going on for several weeks.

"We have been approached by IAEA (International Atomic Energy Agency). The government of Iran gave us some information, which pointed to certain individuals," he said.

He stressed that Dr Khan and other scientists were not detained but only subjected to "de-briefing".

"The government of Pakistan has never proliferated and would never proliferate. Pakistan is a nuclear weapons state and takes its responsibilities seriously," he maintained adding investigators are ascertaining whether the scientists themselves were responsible.

The spokesman also said that Pakistan has not authorised any scientist to collaborate with other countries in the field of nuclear weapons. "This is out of question. Pakistan has a very strong command and control regime and a stringent export control regime.

"If anyone is found to have ignored government instructions, action will be taken and nobody is above the law."

Khan denied this development would prompt Pakistan to sign the Comprehensive Test Ban Treaty (CTBT) but said Pakistan supported Iranian attempts to obtain nuclear technology for peaceful purposes because Tehran is a signatory to the Non Proliferation Treaty (NPT).

In the US, media reports said Dr Khan's investigation by American and European intelligence agencies and international nuclear inspectors has forced Pakistani officials to question his aides and openly confront evidence that the country was the source of crucial technology to enrich uranium for Iran, North Korea and possibly other nations.

New questions about Pakistan's role have also been raised by Libya's decision on December 19 to reveal and dismantle its unconventional weapons, including centrifuges and thousands of centrifuge parts.

There are also investigations underway to determine if Pakistani technology has spread elsewhere in West Asia but so far the evidence largely involves the exchange of scientists with some countries, including Myanmar.

American and European officials say Dr Khan is at the centre of their investigation. A European confidante of Dr Khan told the New York Times that the Pakistani scientist put the blame for the transfers on a West Asian businessman was supplying Pakistan with centrifuge parts and, on his own, double-ordered the same components to sell to Iran.

"There is evidence he is innocent," the confidante said of Dr Khan. "I don't think he is lying, but not perhaps telling the whole truth."