OSAKA, JAPAN, DECEMBER 17

A fire that spread from a fourth-floor mental clinic in an eight-story building in downtown Osaka in western Japan on Friday left 24 dead in what police were treating as a possible case of arson.

Media reports said police were searching for a man who witnesses saw carrying a paper bag from which an unidentified liquid was dripping. The man could have been among the 24 dead, reports said. Police declined to confirm those reports.

Fire officials who reached the building in the major business, shopping and entertainment area of Kitashinchi in Osaka found 27 people in a state of cardiac arrest, said Osaka fire department official Akira Kishimoto.

One woman was conscious and brought down by an aerial ladder from a window on the sixth floor and was being treated in a hospital, he said.

Later Friday, 24 people were pronounced dead, the fire department said. It said three others were resuscitated and are in serious conditions.

In Japan, the authorities customarily describe those without vital signs as being in 'shinpai teishi' or a state of cardiac and pulmonary arrest, and do not confirm deaths until they are pronounced at hospitals and other necessary procedures are done.

A doctor at one of the hospitals treating the victims said he believed many of them died after inhaling carbon monoxide as they had limited external injuries.

Hours later Friday night, crowds were still gathering outside of the building to take a glimpse of the scene where firefighters and police officers were investigating.

'I haven't heard of the cause but I'm shocked and wondering why someone would do this,' said Yuji Uehara, who works for a finance company. 'I also offer my condolences to those who died.'

The building houses the mental and internal medicine clinic, an English language school and other businesses. Most of the victims are believed to be visitors at the clinic on the fourth floor, fire officials said.

The cause of the fire and other details were not immediately known. Osaka police earlier said they were working to determine whether the fire was caused by arson. They later set up a team at the prefectural police headquarters, a sign they strongly suspect arson and murder.

According to NHK, a female outpatient at the clinic's reception desk saw the man being sought by police. Another person nearby said the fire started soon after he put the leaky bag next to a stove on the floor and kicked it, with more of the liquid pouring out.

The clinic's psychiatrist, Kotaro Nishizawa, could not be reached since the fire, NHK said. It quoted his father as saying the doctor hinted at a problem at the clinic but did not elaborate.

People on other floors of the building were believed to have been safely evacuated, fire officials said.

NHK quoted a witness as saying she heard a woman's voice coming from the fourth floor calling for help. Another witness told TV Asahi he saw flames and smoke coming out of windows on the fourth floor when he stepped outside after hearing a commotion.

In total, 70 fire engines were mobilized to fight the fire, which was fully extinguished more than six hours later, officials said.

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, an intentionally set blaze in Tokyo's Kabukicho entertainment district killed 44 people - the country's worst known case of arson in modern times.