Prosecutors on Sunday ended the overnight questioning of Justice Minister Cho Kuk's wife as part of a widening investigation into corruption allegations surrounding the minister's family.

The questioning that started around 9 a.m. Saturday at the Seoul Central District Prosecutors' Office finished at 1:50 a.m. Sunday. It was the fourth time prosecutors had questioned Cho's wife, a university professor surnamed Chung.

The actual interrogation finished before 6 p.m. Saturday, but the session extended into Sunday as Chung's attorney requested additional time to review documents relating to the questioning, according to the prosecution.

Chung faces allegations of forging a college presidential citation to help the couple's daughter gain admission to a medical school. She is also suspected of intervening in a dubious private equity fund investment.

In the fourth interview, Chung was mostly asked about her involvement in the private equity fund in which she and her two children invested a combined 1.05 billion won ($8.85 million) in July 2017.

The timing of the investment, right after Cho's appointment as senior presidential aide for civil affairs, and a jump in government orders for a local manufacturer in which the fund made a hefty investment, coincided, raising suspicions on Cho's possible influence.

Cho has denied any involvement in the private equity fund investment.

Prosecutors also asked Chung about the whereabouts of her laptop, which may hold significant evidence regarding the ongoing probe.

Sources said the prosecution could consider seeking an arrest warrant for Chung this week, but they are likely to review the decision carefully considering how an arrest warrant for Cho's younger brother, who is also facing corruption allegations, was recently rejected by a Seoul court.

The court cited Cho's brother's health as the cause for the rejection. Chung has also claimed to be suffering from poor health and asked to leave the first questioning early on Oct. 3. (Yonhap)