South Korean President Yoon Suk Yeol faces mounting scrutiny as the joint investigation unit probing the Dec. 3 martial law controversy attempted to summon him for questioning on Monday, the same day prosecutors issued a second summons for his appearance.

The joint investigative body, consisting of the Korean National Police Agency’s National Office of Investigation, the Corruption Investigation Office for High-ranking Officials and the Criminal Investigation Command of the Defense Ministry, stated on Monday that it attempted to deliver a questioning summons notice to the presidential office for Yoon’s appearance on Wednesday.

However, authorities told the press that the presidential office declined to cooperate with the investigators, citing the suspension of Yoon’s constitutional duties after the passing of his impeachment bill by the National Assembly on Saturday.

“The Presidential Secretariat stated that it was unclear whether delivering a summons notice during the president’s suspension of duties falls under their responsibilities,” a joint investigation unit official told the press on Monday.

Another team was sent to Yoon’s residence to deliver the summons request as of 11 a.m., Monday. As of press time, whether this summons request was delivered successfully to Yoon is still unclear.

According to authorities, the summons request outlines Yoon’s allegations of abuse of power as the alleged ringleader of an insurrection in relation to his martial law declaration on Dec. 3.

On Sunday, prosecutors stated that Yoon rejected the prosecution’s order to appear for questioning.

The special prosecution team noted that it had sent such a summons to Yoon last Wednesday, asking him to appear at 10 a.m. on Sunday, but Yoon did not attend.

Prosecutors summoned Yoon to appear for questioning again at 2 p.m., Monday.

If Yoon continues to defy orders for questioning, prosecutors or the joint investigation team can seek a court-issued arrest warrant. However, authorities have told the press that such options are not being reviewed yet.

Following Yoon’s declaration of martial law, two investigative bodies began investigating the case, with one led by the police and the other led by prosecutors. Though prosecutors requested the police to conduct a joint investigation into the martial law proclamation on Dec. 6, the police declined, saying that insurrection falls under the “investigative jurisdiction of the police.”

With Yoon impeached as of Saturday, investigations on both sides are beginning to accelerate.

The police attempted to raid the presidential office on Dec. 11 after obtaining a search and seizure warrant listing Yoon as a suspect. However, such seizure attempts have so far failed as the Presidential Security Service did not permit law enforcement to enter the presidential office under the Criminal Procedure Act.

Prosecutors, on the other hand, have taken the lead in detaining key suspects, such as former Defense Minister Kim Yong-hyun and former military counterintelligence chief Yeo In-hyung.