SEOUL, South Korea — Arrested South Korean President Yoon Seok-yeol failed to attend a second day of questioning by investigators on Thursday, further hampering a criminal probe into whether he committed rebellion under martial law.

Yoon on Wednesday became the first sitting South Korean president to be arrested and was taken to a Seoul detention center after refusing to cooperate. He remained at the center Thursday, with his attorney citing his medical condition as a factor.

Authorities have 48 hours to question the suspended president before they must release him or seek a warrant to detain him for up to 20 days.

Yoon's refusal to cooperate with investigators came as the Constitutional Court held a second hearing in his impeachment trial to determine whether to permanently remove him or restore his presidential powers.

South Korea is grappling with its worst political crisis in decades, with Yoon Eun-hye's brief attempt to impose martial law on December 3 only to be rejected by parliament.

During the opening debate of the Constitutional Court, an opposition Democratic lawmaker denounced Yoon's "December 3 rebellion" and said Yoon and a handful of supporters were trying to incite chaos by refusing to accept his arrest warrant.

"This impeachment trial will determine whether such a person should be reinstated as commander-in-chief controlling the military," said Chung Ching Lai, chairman of the parliament's Legislation and Judiciary Committee.

In response, one of Yoon's defense teams stated that the purpose of impeaching Yoon was not to defend the constitution, but to allow the opposition to "use the majority power of the parliament to usurp the presidency."

The main opposition Democratic Party used its majority in parliament to vote on impeachment against Yoon, although about a dozen lawmakers from Yoon's party also voted for impeachment.

Yoon's lawyer, Zhao Daxian, said the suspended president's decision to declare martial law was a well-intentioned decision based on his belief that the country was in a state of emergency.

Another of Yoon's lawyers, Bae Jin-han, quipped: "Now some people say 'You will be impeached if you breathe.'"

Yoon was arrested on Wednesday, ending a week-long standoff with authorities after police raided his hillside villa in Seoul before dawn, leaving followers at the scene desperate.

Yin said he turned himself in for questioning by officials investigating corruption to prevent the risk of what he called "unpleasant bloodshed," although he continued to protest that it was an illegal investigation and an invalid arrest warrant.

An official at the Corruption Investigation Office (CIO), the senior official in charge of the criminal probe, said the embattled leader has so far refused to speak to investigators who have prepared more than 200 pages of questionnaires.

His questioning was scheduled to resume Thursday at 2 p.m. (12 a.m. ET), but the CIO said Yin Fang had informed him that he would not attend.

Yonhap quoted one of Yoon's lawyers as saying the suspended president's health was a factor and further inquiries were pointless, without elaborating.

A small group of pro-Yin protesters gathered on the road outside the chief information officer's office, calling the president's arrest illegal.

His lawyers said the arrest warrant was illegal because it was issued by a court in the wrong jurisdiction and the team set up to investigate him did not have the legal authority to do so.

They also asked another court to review the legality of the arrest. Yin's 48-hour arrest period was temporarily suspended pending court review, according to the CIO.

His legal team has denied accusations that Yoon plotted rebellion, a crime punishable by life in prison and even technically the death penalty in South Korea.

South Korea's last execution was in 1997 for criminal offenses such as murder.