Seven people were killed and a dozen others injured Thursday following a fire at a hotel in Bucheon, Gyeonggi Province, with authorities on Friday strongly suspecting "an electric fault" as the main cause.

The blaze started on the eighth floor of the nine-story building at around 7:39 p.m. at a hotel in Jung-dong, Wonmi-gu, Bucheon, Gyeonggi Province, according to fire authorities.

The fire, which was confined to the hotel’s upper floors, quickly filled the corridors with thick black smoke. Most of the casualties were due to inhalation of toxic smoke, a situation exacerbated by the absence of a sprinkler system, fire authorities said.

Gyeonggi-do Fire Services said in a Friday briefing that they "strongly suspect an electric fault" to be the cause behind the fire.

Among the deceased were four men and three women, ranging in age from their 20s to 50s, all confirmed to be Korean. The victims had primarily been staying on the eighth and ninth floors near room 810 where the fire started.

In an attempt to escape, two guests jumped from their eighth-floor rooms onto an inflatable air mattress outside but tragically lost their lives when the mattress flipped.

Fire authorities confirmed that the hotel, built in 2003, did not have sprinklers installed in the rooms. The building was not subject to the 2017 regulation requiring sprinklers in newly constructed buildings over six floors. Unlike some medical facilities, older buildings are not required to retroactively install them. The absence of this safety measure likely contributed to the heavy toll of the incident, fire authorities said.

The injured, three of whom are in serious condition, are being treated at various hospitals, including Soonchunhyang University Bucheon Hospital.

Interior Minister Lee Sang-min visited the scene Friday morning to assess the situation and oversee the recovery efforts. He called on fire authorities to remain dedicated to extinguishing the fire and rescuing individuals. Lee said, "Firefighting authorities and local governments must utilize all available personnel and equipment to fully focus on firefighting and rescue operations," and urged them to give special attention to the safety of the rescue teams.

Authorities are continuing their investigation to determine the precise origin and cause of the fire. Joint inspections with related agencies are planned to assess the damage and prevent future incidents.