The family of a prominent Pakistani scientist says he is being used as a scapegoat in a row over the alleged transfer of nuclear technology to Iran.
Pakistan says it takes its nuclear responsibility very seriously
The scientist, Abdul Qadeer Khan, played a key role in developing the country's nuclear bomb.
Dr Khan is one of a number of nuclear scientists who have been questioned by Pakistani authorities.
Pakistan launched an investigation following information from Iran and the International Atomic Energy Agency.
Dr Khan's daughter, Dina Khan, told BBC World Service's Newshour programme she was concerned about what would happen to him next.
"My father is being made a scapegoat for the use of other people," Ms Khan said.
"We are getting a lot of shocked reactions. The situation is very strange. We don't really know why it's happening and what's going to happen."
On Tuesday, a Pakistani foreign ministry spokesman said some of its nuclear scientists may have passed sensitive nuclear technology to Iran out of personal greed and ambition.
The spokesman, Masood Khan, said if the allegations were true, legal action would be taken.
He said no Pakistani state institution had ever transferred nuclear know-how, and never would.
But a former head of Pakistani intelligence, Hamid Gul, said it was impossible for eminent nuclear scientists to act independently without detection.
He told the BBC comprehensive security and profiling arrangements follow them through their working lives and beyond into retirement.
On Monday, the government confirmed Dr Khan, the so-called father of Pakistan's nuclear weapons programme, was being questioned.
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.