Umno president Ahmad Zahid Hamidi emerged from the MACC headquarters in Putrajaya at 6.10pm after spending more than nine hours having his statement recorded.
Speaking to reporters, the former deputy premier said he has been asked to return for another round of questioning tomorrow morning.
Accompanied by an aide and a bodyguard, he also thanked media personnel who were camping outside the building.
"I want to say thank-you to all friends from the media who 'bersusah payah' waited for me from morning until evening.
"And I am relieved that there is loyalty from the media. Thank you," he quipped before walking towards his vehicle.
This is the second day in a row that Zahid had been summoned for questioning.
Earlier, a senior MACC investigator told Malaysiakini that the case is being probed under Section 23 of MACC Act 2009 for alleged abuse of power for gratification and criminal breach of trust.
However, the source declined to confirm if this was related to the alleged misappropriation of funds belonging to Akal Budi Foundation or the alleged RM2.6 billion donation by a Saudi royalty that was deposited into former prime minister Najib Abdul Razak's personal bank account.
Contacted later, MACC deputy chief commissioner (operations) Azam Baki told Malaysiakini that Zahid's son-in-law was also summoned to facilitate investigations.
The son-in-law, Saiful Nizam Mohd Yusoff, is the husband of Zahid's daughter Nurul Hidayah, whom Bernama reported had her statement recorded yesterday.
As to what offences Zahid was questioned on, Azam (photo) said: "Of course, when someone is summoned to MACC, it is to assist in our investigations and the offences will be under the MACC Act 2009, and probably related to some other criminal offence."
Azam declined to elaborate.
Yesterday, Zahid was also questioned at the MACC headquarters for about nine hours. Prior to this, he had been called in for questioning twice in July.
The first was on July 2, when he was questioned on issues related to the alleged RM2.6 billion donation.
Previously, Zahid claimed that in 2015, he had met the chief investment officer and wealth trustee of the family behind the donation to Najib.
The Umno president returned to the MACC for the second time on July 3 to have his statement recorded on the alleged misuse of funds belonging to Akal Budi Foundation.
It was reported that RM800,000 from the foundation's funds were allegedly used to pay the credit card bills of Zahid and his wife.