Prosecutors in South Korea on Thursday summoned the country’s former justice minister as they expand an investigation into corruption allegations surrounding his family that sparked huge protests.

Cho Kuk’s questioning at the Seoul Central District Prosecutors’ Office follows the arrests of his wife, brother and another relative over their suspected involvement in financial crimes and faking credentials to help get Cho’s daughter into medical school and obtain scholarships.

Cho, a reformist law professor and confidant of South Korean President Moon Jae-in, resigned as minister last month, citing the burden of the investigation into his family. He has denied any legal wrongdoing while apologising over the perks his daughter is alleged to have received.

“I will soon be investigated by prosecutors. Everything about me will come under suspicion and I might get into trouble for things that I didn’t know about or don’t remember,” Cho wrote on Facebook on Monday. “I feel miserable, but I will invest every effort to establish the truth and restore my honour.”

Huge crowds of Cho’s supporters and critics have marched in Seoul for weeks, demonstrating how the months-long saga has deepened the country’s political divide.

Before Cho’s resignation, Moon stood firmly by the key political ally he appointed in September despite parliamentary resistance.

But the controversy surrounding Cho has caused the president’s popularity to slide.

Prosecutors last month arrested Cho’s university professor wife, Chung Kyung-shim, who has been indicted over her suspected involvement in dubious private equity investments and faking materials to help their daughter’s admission to a medical school in Busan.