Prime Minister Lee Nak-yon paid his respects on Sunday to the victims of a fitness center fire in the central city of Jecheon which left 29 people dead and scores injured.
Lee visited the gutted eight-story building and the disaster situation room in the city hall and later met with injured survivors and families of those killed in one of the worst fire disasters in the nation.
He pledged to take lessons from the incident and enhance the nation's safety system.
"As a man responsible for state affairs, I am at a loss for words," Lee said during a meeting with disaster response officials. "We will take this painful lesson to more closely examine systems and ensure improvements."
Authorities said the Thursday fire started from the ceiling of a parking lot on the ground floor and quickly spread through the building.
Witnesses said fire alarms, emergency lamps and sprinklers were not working at the time of the accident. Firefighters were under fire for delayed rescue operations and failure to break windows and enter the second floor, where 20 of the 29 victims were trapped in a women's sauna.
The prime minister ordered a thorough probe into the cause of the fire while calling for the fire fighters' efforts to be assessed fairly.
"Aside from the investigation into the cause and possible punishments, the dedication and efforts of firefighters who risked their lives to extinguish the fire and save lives deserve due assessment."
Lee also visited a hospital to meet injured people including an elderly man who rescued 15 people at the scene.
The leaders of ruling and opposition parties also visited Jecheon and paid their tributes at the altar for the victims.
On Sunday night, police detained the 53-year-old owner of the building and the 50-year-old janitor over charges of alleged professional negligence and violating fire safety laws.
Police found that the second-floor door to emergency stairs was blocked at the time of the fire.
Also, some fire sprinklers on the first-floor parking lot did not activate as the fire erupted, according to police.
Investigation showed that two terraces were illegally built on the two top floors.
It was originally a seven-story building and two stories were added in 2012 and 2013. The former owner of the property built two terraces covered with flammable materials on the eighth and ninth floors without permission.
The terraces appeared to have caused flames to spread to the top floors quickly, fire authorities said.
The current owner bought the building in August. (Yonhap)