At least 24 people are feared dead in a suspected arson attack on an animation company in the Japanese city of Kyoto on Thursday, a fire department official said.

The official said one person had been found on the second floor of the building "in cardio-respiratory arrest," a term used in Japan to signify a victim's death before it is officially certified.

The official said "10 or more people" were found in the same condition on the stairs from the second floor to the roof, bringing the total toll in the blaze so far to at least 24.