The country had its first fire of the Christmas season when an overheated extension cord ignited a tree at a home in Barrio la Colina in Tirrases de Curridabat.
A man, 57, and a women, 58, suffered first- and second-degree burns and were hospitalized.
The Cuerpo de Bomberos reported some damage to the home and the ceiling above the tree.
And there was a greater area with smoke damage.
The fire brought an unusual Sunday night warning from the fire fighting agency.
There have been one or two Christmas tree fires each year since 2010, the agency said, adding the the main causes were electrical.
In the case of the Sunday night fire, the extension cord was not certified by the Underwriters Laboratory or similar, the agency said.
The fire agency said that residents should make sure that such cords and tree lights are certified. The danger also exists with the portales or nativity scenes that are erected within homes at this time of year. They have been sources of fires, too. the agency said.
Héctor Chaves, director general of the Cuerpo de Bomberos, also urged residents to extinguish Christmas lights before going to bed and to make sure not to overload electrical circuits.