A man was arrested Thursday on suspicion of causing an explosion that led to a fire at a dental clinic in Gwangju, some 270 kilometers south of Seoul.

The suspect, 79, brought a makeshift explosive comprised of four canisters of butane gas and a container with flammable material to the reception area of the clinic, located on the third floor of a building in Seo-gu, western Gwangju. He set fire to the material at 1:14 p.m. Thursday, setting off a chain of explosions that forced some 90 people to evacuate from the building.

The fire was extinguished after nine minutes by the sprinkler system, and no casualties occurred.

Police revealed in a press briefing that the suspect was a patient at the clinic, but said it is still unclear why he committed the crime.

The suspect fled the scene in a taxi toward his home but then changed the destination to Gwangsan Police Station, where he was apprehended by police at around 3 p.m. He claimed that he came to the station to turn himself in.

Officials are holding him for further questioning, including concerning the motive for the crime. He is being investigated for violating Article 164 of the Criminal Act, which stipulates that a person who sets fire to a building in current use shall be punished by a sentence of three years to life in prison.