(CNN) -- At least 46 people died and dozens were injured after a major fire broke out in a building in southern Taiwan on Thursday, authorities said.
The blaze started in the 13-story commercial and residential building at 2:54 a.m. local time (2:54 p.m. ET) in Kaohsiung city's Yancheng district, according to Taiwan's official Central News Agency (CNA).
Rescue operations are still underway, with more than 377 rescue workers deployed to the scene, a spokesman at the Kaohsiung city fire bureau told CNN. At least 41 people have suffered injuries, he said.
Initially, authorities put the death toll at seven, but the city's fire chief Lee Ching-hsiu warned more casualties were expected as some people may still be trapped in the residential part of the building, between the seventh and eleventh floors.
A total of 139 fire trucks and ambulances were deployed to the scene and extinguished the fire by 7:17 a.m. (7:17 pm ET), CNA said. By midday, at least 62 people between the ages of 8 and 83 had been rescued.
More than 100 residents, many of them senior citizens with physical disabilities, live in the building, according to CNA.
It is unclear what caused the fire, according to CNA. Local police are reviewing surveillance footage and said they cannot rule out human factors, according to the report.
Lee told CNA the number of casualties was high due to a combination of factors: The fire happened overnight; the majority of residents were elderly; the stairwells were full of debris; and the building materials did not meet fire safety standards.
Kaohsiung mayor Chen Chi-mai apologized at an evening news conference.
He explained that the first six floors of the building were built for commercial use, with the seventh floor and above for housing.
While there were no longer any businesses on the first six floors, there were a number of flammable items there. This was one of the main reasons for the heavy casualties, said Chen.
Taiwan's President Tsai Ing-wen expressed her "deepest condolences" to the victims of the fire in a Facebook post.
Tsai promised that her government will "spare the most efforts" to rescue those who are trapped, resettle the residents affected by the fires, and provide necessary assistance to families of victims.
"Facing this serious accident, we extend our deepest condolences to the victims, and we wish the injured a speedy recovery," she wrote on Thursday afternoon local time.
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