Former prime minister Nawaz Sharif and his two sons, Hassan and Hussain, failed to appear before the National Accountability Bureau’s (NAB) Lahore office on Friday for a probe meeting pertaining to a Supreme Court-ordered investigation into the Sharif family's business concerns.

Security had been tightened in and around the NAB office, DawnNews reported, with about 200 police personnel deployed in the surrounding area in anticipation of the ousted PM's visit, but Sharif and his sons did not appear today.

Subsequently, the five-member NAB team comprising an additional director, a deputy director, and an assistant director, returned to Rawalpindi.

NAB sources said a decision on whether or not to send another notice to the family would be made after consultation with the NAB chairman. It also remains to be seen whether Sharif and his sons will be summoned to the offices in Lahore or Islamabad.

PML-N insiders earlier told Dawn that Sharif and his sons would ─ after discussion with close aides and their legal team ─ not join the NAB investigation until the apex court decided on his review petition against the July 28 Panamagate verdict which disqualified him from office.

Explore: Sharif, sons to skip NAB probe meeting today

"Mian Nawaz Sharif and his children have decided not to appear before NAB till a verdict on his review petition in the SC is decided. Sharif has sought a stay of the NAB proceedings and till the apex court decides his petition there is no point in his joining the NAB investigation in cases against him," a close aide to Sharif, who is privy to the development, told Dawn on Thursday.

Sharif appealed to the SC to stay further implementation of the Panamagate judgement, which included orders for the opening of references against the family's Al-Azizia Steel Mills and Hill Metal Establishment, and one regarding 16 other companies.

The companies are Flagship Investments, Hartstone Properties, Que Holdings, Quint Eaton Place 2, Quint Saloane, Quaint, Flagship Securities, Quint Gloucester Place, Quint Paddington, Flagship Developments, Alanna Services (BVI), Lankin SA (BVI), Chadron, Ansbacher, Coomber and Capital FZE (Dubai).

Read more: Panamagate: Decision to disqualify me had been taken before the judgement, Nawaz alleges

PML-N's Senator Asif Kirmani, a close aide of the ex-PM, also said neither Sharif nor his sons would appear before NAB in Lahore, and had not received any summons from NAB.

A joint team of NAB officials from Lahore and Rawalpindi have also formulated a questionnaire for the investigation.

According to a copy of the questionnaire acquired by DawnNews, it is expected that Sharif and his sons will be questioned about financial matters pertaining to Al-Azizia Steel Mills and Hill Metal Establishment.

The inquiry may include questions about the purchase of land and machinery for Al-Azizia, and the formation of its internal structure. NAB is also expected to ask for proof of purchase of machinery for the mill from Dubai.

The probe team could possibly ask about where the capital for the creation of Hill Metal came from, who was part of the board of directors, and where the shareholder details of the company are.

Additionally, the three may be quizzed about the nature of monetary gifts made to Nawaz Sharif by his son Hussain Nawaz.

It is possible that Rehman Malik and Shahbaz Sharif may also be summoned by NAB to record their statements.

As Sharif and his sons failed to appear before NAB today, a second summons may be issued within the next week or so. A third summons may also be issued if they do not appear before the NAB after the second notice, Dawn reported, added that following this course of action may be a way for the Sharif family to buy some time if the review petition before the SC is not in their favour.

With additional reporting by Zulqernain Tahir.