At least 24 people were killed after a fire broke out Friday morning in a building in the Japanese city of Osaka, according to local police. 

The fire erupted at around 10:20 a.m. in a medical clinic on the fourth floor of the eight-storey building located near the JR Osaka Station. The clinic provides psychosomatic and psychiatric treatments.

According to police and fire departments, the victims suffered from carbon monoxide poisoning rather than burns. 

"I saw smoke coming out and there were a lot of fire trucks and ambulances. People were being rescued by a ladder truck. At one point, there was a power outage in the surrounding area," a witness working at a nearby restaurant said. 

TV footage showed dozens of firefighters working inside and outside the narrow office building after the blaze was largely extinguished.

As of 1:20 p.m. local time, the blaze was not entirely put out but was not spreading, the department told China Media Group.

An Osaka police spokesman told AFP that officers were investigating the cause of the fire. But he could not confirm a report by public broadcaster NHK citing police sources as saying there was the "possibility of an arson attack, given the circumstances at the scene."

The Chinese Consulate-General in Osaka said it hasn't received a death or injury report involving Chinese citizens.

(With input from agencies)