President Yoon Suk Yeol arrives at the Corruption Investigation Office for High-ranking Officials building in Gwacheon, Jan. 15. Yonhap

Law enforcement officials were expected to conduct an intense grilling of impeached President Yoon Suk Yeol to delve into allegations that he was the mastermind behind the Dec. 3 martial law attempt that plunged the country into an unprecedented political chaos.

The Corruption Investigation Office for High-ranking Officials (CIO) began its interrogation of Yoon at 11 a.m. Wednesday, hours after it succeeded in executing the court warrant to detain him following a thwarted attempt earlier this month.

The CIO will have up to 48 hours to question Yoon under the warrant issued for his temporary pretrial detention, before it decides whether to seek his arrest, a step it is widely expected to take once the interrogation ends.

The interrogation, with over 200 pages of questions prepared, is expected to focus on substantiating key allegations surrounding the failed martial law imposition, ranging from the planning stages leading up to the event to its execution on the day.

The CIO has been investigating Yoon for actions that may amount to insurrection, abuse of power and other charges.

At the center of the allegations is the question of whether Yoon ordered the military and police to drag a handful of lawmakers out of the National Assembly building on the night he declared martial law and arrest them.

Prosecutors suspect Yoon made the order to lock down parliament to prevent opposition lawmakers from entering the compound to vote to stop the martial law.

The indictment against the now-arrested former Defense Minister Kim Yong-hyun shows the prosecution alleging that Yoon ordered the capital defense commander to "shoot if necessary, break the windows and drag them out."

Yoon is suspected of having named the politicians that they must arrest. National Assembly Speaker Woo Won-shik, Democratic Party of Korea leader Lee Jae-myung and Han Dong-hoon, the then leader of the ruling People Power Party, were allegedly among the list.

A vehicle carrying President Yoon Suk Yeol arrives at the Corruption Investigation Office for High-ranking Officials building in Gwacheon, Jan. 15. Yonhap

Prosecutors have secured a testimony from Hong Jang-won, one of the deputy spy chiefs at the time, claiming that Yoon told him over the phone to "round everybody up."

Military officers questioned by the prosecution have said that they were told to arrest 14 key figures and hold them at an underground bunker near the Capital Defense Command in southwestern Seoul.

The CIO is also likely to question Yoon to determine whether he deployed the military to seize the main network servers at the National Election Commission over what Yoon has called "election fraud" -- one of the reasons he cited for imposing martial law.

The CIO believes Yoon sought to establish an extraordinary legislature to replace the opposition-controlled parliament that has blocked him from pursuing his agenda. It suspects that Yoon also considered imposing another martial law after the Assembly voted to lift the order.

Prosecutors were expected to press Yoon to find out how he orchestrated the martial law from the start.

The opposition parties have alleged that Yoon discussed martial law plans with Kim, the former defense minister, and Yeo In-hyung, the counterintelligence commander, as early as in August last year.

The CIO is expected to question Yoon about how the martial law decree was drafted. The decree banned political activities by parliament and parties, a clause that has been criticized by the opposition and critics as a violation of the Constitution.

Suspicions over whether Yoon lawfully proceeded with the martial law declaration will also likely be a key focus of the interrogation.

Under the Constitution, the president is entitled to declare a state of emergency during wartime or a national emergency or crisis equivalent to such situations. Critics have argued that Yoon's martial law did not meet these standards.

Yoon has justified his martial law as a measure to defend the country from "anti-state forces" that are plundering the country's freedom and to protect the constitutional order.

The CIO suspects that Yoon's decision was intended to paralyze the functions of the Assembly in order to relieve the political pressure he was facing from opposition parties.

Yoon needed a Cabinet review and two-thirds approval from his Cabinet members in order to declare the martial law.

Through questioning the ministers who attended the Dec. 3 Cabinet meeting, the CIO has determined that Yoon did not inform them in advance about the purpose of the meeting, only notifying them on the spot that he would be declaring martial law shortly. (Yonhap)