"A total of eight people have been called in for debriefing sessions, including three retired military officials associated with the Kahuta Research Laboratory (KRL)," a senior official said late Sunday.
"The debriefing sessions are being held in the light of reports received from the International Atomic Energy Agency (IAEA)," said the official, who did not want to be named.
Information Minister Sheikh Rashid confirmed the number but described it as "routine debriefing" sessions.
The officials summoned include Major Islam ul-Haq, senior aide of top Pakistani nuclear scientist Abdul Qadeer Khan, the official confirmed.
"Major Islam ul-Haq was picked up by the security officials from the residence of Doctor Qadeer Khan at about 8:30 pm (1530 GMT) on Saturday," his wife Nilofer told AFP earlier.
Islam, a retired member of the military, is the principal staff officer of Qadeer Khan, who created Pakistan's nuclear bomb.
"Some army officers, including members of the military intelligence, came in two jeeps and said they want to take Major Islam for interrogation," Nilofer said.
Qadeer Khan headed KRL, the country's uranium enrichment facility near Islamabad, until retiring in 2002.
Two KRL directors, Yasin Chohan and Farooq Mohammad, were taken from their homes in December for questioning.
Chohan has since returned home but Farooq is still being questioned.
Qadeer Khan had also been questioned earlier but officials denied his movements were restricted.
Foreign office spokesman Masood Khan said last month that "a very small number" of scientists were being questioned over allegations of leaking nuclear information to Iran and a subsequent request from the nuclear watchdog IAEA to Pakistan for co-operation.
The spokesman said Pakistan had placed some senior nuclear scientists under investigation because of information that they may have co-operated with Iran's nuclear programme for "personal ambition or greed".
Pakistan became a nuclear power in May 1998 when it conducted underground nuclear tests. But it has consistently denied reports that it has exported its nuclear know-how to any other country.