Japanese police on Sunday identified a 61-year-old patient as a prime suspect after a fire engulfed a psychiatric clinic in an eight-storey building, killing 24 people trapped inside. Morio Tanimoto is in a serious condition after he was rescued from the fire, police said. He has not been formally arrested or charged. Police verified security camera footage and searched Mr Tanimoto's home. They suspect he was responsible for setting fire to the clinic, where he was being treated, after they found his patient card, an official at the prefectural police investigation department told AP on condition of anonymity because he was not authorised to speak to the media. Mr Tanimoto is believed to be among the three people who survived the blaze and were in a serious condition. Police have not made any arrests, and it may take time until the man recovers enough to be interrogated. The government also announced plans to inspect tens of thousands of similar buildings nationwide. Authorities believe the huge death toll at the building in downtown Osaka on Friday was largely because the fire made its only emergency stairway unusable. According to witnesses interviewed by Japanese media, a man walked into the clinic, carrying a paper bag, which he put on the floor, right next to a heater by the reception desk, and kicked it. A liquid poured out, caught fire and the whole floor was engulfed in flames and smoke. Witness accounts suggested that the victims gasped for air and struggled to find their way out of the clinic. There was only one way to escape because the lift and emergency stairs were both outside, the authorities said. Police and fire officials on Saturday returned to the site in the middle of Osaka’s Kitashinchi business district. Some experts were surprised by the death toll in a daytime fire that was largely put out within an hour. The authorities are investigating how smoke filled the floor so quickly and how the victims became trapped. There were no prior breaches of fire prevention codes at the building, officials said. There was no emergency exit in the clinic. The office had several compartments for consultations and workshops along just one aisle, with the main counselling room being at the far end of the floor. One of the visitors who witnessed the beginning of the fire at the reception desk was able to run out. It was not yet known exactly how many people were inside the clinic, the investigator said. Kyodo News said Mr Tanimoto was a retired metal worker. His former employer at the factory where he worked from 2002 to 2010 described him as diligent and skilled. He left his job without saying what he was going to do next, he said. Mr Tanimoto trained at his father’s sheet metal factory in Osaka after finishing high school, but left after his brother took over the business, and kept changing jobs, Kyodo said. Locals brought flowers, bottled water and canned drinks as offerings to the spirits of the departed outside the building. Retiree Seki Kageyama, 77, who lives in the neighbourhood, returned to the site after finding out about the large number of dead from what he thought was a minor fire. A sign advertising the burnt-out clinic on the fourth floor still stood, reading: “Nishi Umeda clinic for the mind and body of workers.” “I thought a small fire broke out,” said Mr Kageyama. “I was really stunned when I heard that someone set a fire and killed people there.” More than 70 fire engines and ambulances took part in extinguishing the blaze on Friday morning. Firefighters initially found 27 people in a state of cardiac arrest, including three who were resuscitated at hospitals, according to the Osaka city fire department. One woman was brought down by a ladder from a window on the sixth floor. Some of the clinic's clients who spoke to Japanese media said the centre was popular and was always crowded, with up to 20 people waiting, especially on Fridays when special counselling and programmes were available for those preparing to return to work after sick leave. The clinic’s psychiatrist, Kotaro Nishizawa, could not be reached after the fire. In 2019 at the Kyoto Animation studio, an attacker stormed into the building and set it on fire, killing 36 people and injuring more than 30 others. The incident shocked Japan and drew an outpouring of grief from anime fans worldwide. In 2001, a blaze set deliberately in Tokyo’s Kabukicho entertainment district killed 44 — the country’s worst known case of arson in modern times.