Inmates of Barranquilla's Modelo prison started the fire January 27, setting alight mattresses during a fight between rival gangs.
Authorities reported the deaths of 10 inmates at the time, but six more have died of their injuries since the weekend.
"Two died today from serious burns and respiratory problems," the Caribbean city's health department said in a statement.
It said burn victims were especially vulnerable to infections and other complications.
It was the worst prison incident in Colombia in 14 years.
