The CIO said this week that a summons was sent to Yoon but returned “undelivered” after an unidentified person at the presidential office refused to accept it.
Yoon’s no-show on Wednesday “will be considered as a failure to comply with the first summons”, a CIO statement said.
Investigators said they were considering despatching a second summons, but CIO chief Oh Dong-woon told parliament on Tuesday they were also “reviewing” whether to issue an arrest warrant.
Yoon is being investigated by South Korean prosecutors as well as a joint team of police, defence ministry and anti-corruption investigators.
The president and some of his inner circle face possible life imprisonment, or even the death penalty, if found guilty. He remains under an international travel ban.
South Korea’s Constitutional Court, which began proceedings against Yoon on Monday, is separately deliberating whether to uphold his impeachment.
The court on Wednesday ordered Yoon to submit the martial law decree he issued two weeks ago, as well as the records of cabinet meetings held directly before and after the announcement.
The judges have about six months to decide Yoon’s case and a preliminary hearing has been set for Dec 27, although Yoon is not required to attend.
