Pakistan has extended an investigation into the possible illegal transfer of nuclear technology to Iran by taking in five more people for questioning.
Pakistan denies any state involvement in technology transfers
Two scientists and three officials linked to an uranium enrichment plant were "debriefed" over the weekend.
Pakistan began a probe last month following information from Iran and the International Atomic Energy Agency.
It has admitted some scientists may have passed nuclear technology to Iran out of personal greed and ambition.
Foreign ministry spokesman Masood Khan appeared at a news conference on Monday to stress again that the government had not shared nuclear technology with Iran or other countries such as North Korea and Libya.
Mr Khan also said the round of questioning would soon be completed.
Mr Khan said: "The government of Pakistan has never proliferated and will never proliferate. No government institution or entity has ever been involved in any such alleged transactions or transfers."
He added: "We are moving towards the conclusion of these debriefings... There is no presumption of guilt. It is
probable that some of these people will be cleared."
Mr Khan said the investigation had shown there was a "black market" and that "we should all work to eliminate that black market".
One of those reportedly taken over the weekend was Major Islam ul-Haq.
Nuclear pioneer Abdul Qadeer Khan, who was questioned last month
He was the principal staff officer of Abdul Qadeer Khan at the uranium enrichment plant Kahuta Research Laboratories.
Mr Khan, credited as the father of Pakistan's nuclear programme, was one of those questioned last month.
He has not been detained and is still treated as a hero by many Pakistanis.
Last month, the foreign ministry promised legal action against anyone thought to have passed sensitive information.
The United States has long been concerned about the transfer of nuclear technology to countries it dubs "rogue states".
The New York Times reported last month that Iran had given information to the IAEA, strengthening suspicion that Pakistan had transferred sensitive nuclear information to Tehran.
US officials also suspect that Pakistan was a source of nuclear technology for Libya.
Libya has promised to give up its nuclear programme and reveal its sources.