TOKYO — A 61-year-old man whom the police suspected of setting the fire that killed 25 people this month at a psychiatric clinic in Osaka has died in a hospital, where he had been receiving treatment for smoke inhalation.
Surveillance footage put the suspect, Morio Tanimoto, at the clinic just before the fire started on Dec. 17, according to the police. Cameras captured him earlier leaving his home on a bicycle, carrying two large bags that the police believe contained gasoline.
Footage that morning from the clinic, on the fourth floor of a busy downtown office building, shows a man believed to be Mr. Tanimoto setting two bags on the floor of the waiting area, an instant before the fire starts.
Mr. Tanimoto was among 28 people hospitalized after the blaze. He died on Thursday of carbon monoxide poisoning, according to NHK, Japan’s national broadcaster.
Mr. Tanimoto had not been charged with a crime. Despite his death, the police intend to continue their investigation and to refer the case to prosecutors, the broadcaster said.
The police have not said what they believe the motive may have been. Investigators found newspaper clippings about previous cases of arson in Japan at Mr. Tanimoto’s apartment, NHK reported, and the police have indicated that a document also found there suggested that he had a connection to the clinic.
The clinic’s building had only one emergency staircase, and the victims, unable to flee, were exposed to large quantities of smoke and carbon monoxide. After the fire, officials in Osaka carried out an urgent campaign to inspect buildings with just one set of stairs to ensure that exits were not blocked.
The fire shocked Japan, a country where violent crime is rare. Just six weeks earlier, police said that a man dressed as the Joker had wounded 17 people with a knife on a Tokyo train and tried to set it afire. In November, a man was arrested after a fire was set on a bullet train in southern Japan.
The fire in Osaka, Japan’s third-largest city, was the deadliest in Japan since 2019, when an arson fire at a Kyoto animation studio killed 33 people. That blaze also raised concerns about the safety of some older buildings.
Mr. Tanimoto was the 26th person to die from injuries sustained in the Osaka fire. The clinic’s director was among those who perished. One survivor is still hospitalized in serious condition, NHK said.