Police on Tuesday opened an investigation into the cause of a huge fire that engulfed a 21-story hotel in Cheonan, about 90 kilometers south of Seoul, the previous day, leaving one employee dead and 19 others injured.

The Cheonan Seobuk Police Station said it has secured videos from surveillance cameras installed inside the Ramada Encore Hotel and in neighboring buildings to look for clues to the cause of the fire.

A 53-year-old hotel worker surnamed Kim was found dead in the first basement of the hotel, while 19 people, including four firefighters, suffered smoke inhalation.

Meanwhile, it has been disclosed that safety inspectors found a defective sprinkler at the hotel in July last year, according to officials at the Cheonan Seobuk Fire Station.

The hotel was notified of the problem and later reported its repair to the fire station, the officials said.

But police and firefighters suspect that the fire may have started due to malfunctioning or poor repairs of sprinklers installed on the ceiling of each floor.

"There is a high possibility that the sprinklers didn't work as the smoke kept rising up from the underground floors," a firefighter said.

The fire believed to have started in the basement was put out after four hours. The hotel, which has 420 rooms, opened in September last year.

Police said they are having difficulty securing testimony from first witnesses, as Kim is believed to be the first person to report the fire to the fire station.

The owner of the hotel reportedly told police he was inside the hotel at the time of the fire but didn't know the cause.

Police said their investigation will focus on whether the hotel owner violated building and fire codes. (Yonhap)