A fire has killed at least 46 after blazing through a 13-story apartment building in Taiwan early Thursday. The cause of the fire is under investigation, according to the city’s fire chief. Firefighters extinguished the inferno after battling it for four hours. “It was a sea of flames,” Lin Chuan-fu, a Kaohsiung resident, told The New York Times. He said a loud explosion had woken him up around 3 a.m. The blaze marks Taiwan’s deadliest building fire since a 1995 incident in a karaoke club that killed 64.

The apartment complex was located in central Kaohsiung, Taiwan’s third-biggest city. The once-bustling building was partially abandoned after a smaller fire in 1999. It subsequently became known by residents as the city’s “No. 1 ghost building” after squatters and gamblers began to move in. The Times reported the building was occupied largely by low-income and elderly residents, making up roughly 120 families. The newspaper also noted what appeared to be the building’s “alarming safety conditions,” including piles of debris obstructing stairwells, corroded pipes, and exposed wires.