ISLAMABAD, Pakistan  —  Pakistan (search) is investigating whether scientists participating in its nuclear program were involved in the proliferation of sensitive technology, the government's top spokesman said Monday.

Pakistan's government has strongly denied allegations it spread nuclear technology to countries such as Iran and North Korea (search) — but appeared to acknowledge Monday the possibility that individual scientists may have acted without authorization.

"Some individuals may have been doing something on their own. We are investigating that," Information Minister Sheikh Rashid Ahmed told The Associated Press.

At least two scientists from Khan Research Laboratories, the country's top nuclear laboratory, have been held for questioning this month, including Mohammad Farooq (search), its former director general.

Officials have declined to give details about the "in-house" investigations and what allegations the scientists faced.

One of the scientists has been allowed to return home, but Khan, an aide to the founder of Pakistan's nuclear weapons program, Abdul Qadeer Khan, is still in custody.

"Dr. Farooq is still undergoing a dependability and debriefing session," said Foreign Ministry spokesman Masood Khan.

Pakistan, which carried out nuclear weapons tests in 1998, "takes its responsibilities as a nuclear weapons state very seriously," he said.

"The government of Pakistan has not authorized any transfers of sensitive nuclear technology to other countries. We have a strong command and control system. Only individuals are being investigated," he said.

Ahmed said investigations followed "IAEA reservations and recent news reports in the Western world."

According to diplomats, the Vienna-based International Atomic Energy Agency (search) has identified Russia, China and Pakistan as probable sources for equipment used by Iran for possible nuclear weapons development.

This month, Iran signed a key accord Thursday that gives U.N. experts full access to its nuclear facilities. That followed international pressure on Iran to prove it had not tried to build atomic weapons.

Recent newspaper reports have suggested that some of Iran's technology, such as designs for centrifuges used for enriching uranium, may have been come from Pakistan. Pakistan has also been accused of exchanging nuclear know-how with communist North Korea in return for missiles.

Pakistan's President Gen. Pervez Musharraf said last month that his country obtained short-range missiles and technology from North Korea, but denied giving any nuclear weapons secrets in return.

Khan Research Laboratories is Pakistan's main nuclear weapons laboratory where uranium is enriched, according to the Federation of American Scientists.

Last year, Pakistan detained a former nuclear scientist Sultan Bashiruddin Mehmood on suspicion of his links with Usama bin Laden.

Mehmood, who worked for Pakistan's Atomic Energy Commission until his retirement in 1999, was later freed.