Public Funds Prosecution started investigating presidential candidate Ahmed Shafiq
's graft case on Monday evening.
Last week MP Essam Sultan accused Mubarak's last prime minister of squandering public funds and facilitating the sale of 40,000 metres of land for Alaa Mubarak and Gamal Mubarak, the sons of former president Mubarak.
Sultan gave testimony to the Public Funds Prosecution on Monday.
He accused Shafiq of selling the land for 75 piastres per metre instead of LE8 per metre and exploiting his position as head of the Young Air Force Officers Association by selling thousands of acres of state land in Ismailiya in 1993.
Shafiq refuted the accusations at a press conference on Monday held at Shafiq's villa in the Dokki district of Cairo.
Shafiq slammed Sultan, saying he was a former state security informant, who now dedicates a significant amount of time and effort to tarnishing Shafiq's image during the ongoing presidential polls.
Three weeks ago, Shafiq was charged with 35 charges of corruption and squandering public money.
Egypt's first post-Mubarak presidential poll will be held on 23 and 24 May, with a runoff vote if necessary on 16 and 17 June.