A union of fire department workers filed a complaint against Interior Minister Lee Sang-min, alleging he failed to perform his duties regarding the crowd surge in Itaewon that has taken the lives of at least 158 people.

The union filed a complaint against Lee on Monday on charges including dereliction of duty and professional negligence resulting in death to the special investigation division set up by the National Police Agency to look into the tragedy.

"The special investigation division should immediately book Lee for an investigation," the union said in a press conference Monday. "We request that Lee admits his responsibilities in the Itaewon tragedy and resign."

The union called out the division for naming officials who responded to the incident on the scene as suspects and leaving out high-ranking officials who are responsible for the prevention of such incidents.

The union was enraged after Yongsan Fire Chief Choi Seong-beom was booked as a suspect on an allegation of professional negligence for his response to the tragedy.

Though the independent investigative division has been looking into the responsibilities of officials from the police, fire department, Yongsan-gu Office and Seoul Metro, it has not yet conducted an investigation into the Interior Ministry, which is in charge of monitoring the safety of the nation.

The union claimed Lee is responsible for the tragedy as it happened because the nation’s disaster management and preventive measures were insufficient.

"We have been conducting the needed investigation on Lee, reviewing the relevant laws," Kim Dong-wook, spokesperson for the investigation division, said Monday, though he refused to delve further into details.

Lee has remained firm in his stance that he will not resign over the tragedy.

“I can fulfill my duties best by doing the best I can in my own seat,” Lee said at a National Assembly meeting held Monday, after being called out by the main opposition Democratic Party of Korea’s resignation requests.

“I will not let the people down and do my best to gather the capabilities of the Interior Ministry within my power and efforts on a pangovernmental level,” Lee said. “I will do everything I can to make a country that the people can feel safe in as they carry out their daily lives, not a dangerous one.”