Lee Ming-feng, director of the Tainan City Fire Department, said crews pulled 115 people -- 69 patients with chronic diseases and 46 mental health patients -- from the fire, Taiwan's Central News Agency in Taiwan reported.
The fire at the Beimen Branch of the state-operated Sinying Hospital, was extinguished in less than an hour, Lee said. The facility in Tainan specializes in caring for people with chronic diseases or mental health issues who cannot care for themselves.
An initial investigation indicated the fire likely started in an empty ward, the Central News Agency said.
President Ma Ying-jeou expressed condolences to the families of the 12 patients who died. He also asked that the Health Department provide the "best possible" treatment and follow-up care to the other patients who were injured in the fire.
Firefighters said most patients were seriously ill and couldn't move on their own, which prolonged the evacuation process.