SEOUL, South Korea (AP) — Twenty-one people suffocated and seven people were injured Wednesday in a fire at a hospital in southern South Korea that specializes in patients suffering from dementia and palsy, officials said.

One patient at the Hyosarang Hospital in Jangseong county, an 81-year-old man suffering from dementia, was detained in an investigation after security video footage showed him entering an area where the blaze began, police said. Police declined to provide further details, saying the cause of the fire was still being investigated.