Japanese police said they were investigating whether the blaze was caused by arson or an accident.
At least 24 people have died after a fire broke out in a building in Osaka in western Japan on Friday.
Police have confirmed they are investigating arson as a possible cause of the blaze, which occurred at a fourth-floor clinic.
Officials were alerted to a fire at an eight-story building in the shopping and entertainment area of Kitashinchi, Osaka city fire department official Akira Kishimoto said.
A total of 27 people were found in a state of cardiac arrest, Kishimoto added.
Later on Friday, 24 people were pronounced dead, while three others were resuscitated and are in serious conditions.
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, Kishimoto said.
People on other floors of the building were believed to have been evacuated, officials also stated.
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.
The building in Osaka houses an internal medicine clinic, an English language school, and other businesses, according to NHK national television.
NHK footage showed dozens of fire engines and police vehicles on the street near the building, with onlookers watching the development from across the street.
One witness told TV Asahi he saw orange flames and grey smoke coming out of windows on the fourth floor of the building when he stepped outside after hearing a commotion.
In all, 70 fire engines were mobilised to fight the fire, which was mostly extinguished within about 30 minutes of an emergency call, officials said.
In 2019, an arson attack stormed at the Kyoto Animation studio killed 36 people and injured more than 30 others.