Pakistani Foreign Ministry spokesman Masood Khan says authorities are nearing the end of their investigation but refused to comment on the results.

"We have not made a final determination yet. The investigation is continuing. We are moving towards conclusion of these debriefing sessions."

Earlier in the day, Information Minister Sheikh Rashid Ahmed told local media that no evidence has been found that Pakistani scientists passed nuclear weapon technology to other countries. Authorities began questioning nuclear scientists and officials associated with the country's top nuclear facility nearly two months ago.

Pakistan says the probe is a response to questions by the International Atomic Energy Agency. The U.N. agency is investigating claims that Iran received help from Pakistan or other countries in attempting to develop its nuclear program.

The spokesman, Mr. Khan, again denied official involvement with the Iranian nuclear program. "No government institution or entity has ever been involved in any such transactions or transfers," he said.

But he did not rule out the possibility that individuals may have passed on nuclear know-how for personal gain.

Relatives of those detained say they are worried and that they have not been allowed to contact them.

Dr. Shafiq Khan is the son of one of those being questioned. "We are at a loss. We have absolutely no idea why he was arrested along with the other guys. We just do not know," he said.

A close aide to Abdul-Qadeer Khan, the creator of Pakistan's nuclear-weapons program, was also among those taken into custody for questioning.