The "careless use of electricity" by the Ruyi Inn's manager surnamed Tang led to the electrical fault, a spokesman with the fire-fighting and disaster-relief headquarters said.
The blaze broke out in the inn in Dukezong Ancient Town after an electrical fault set a curtain on fire, according to the result of a preliminary investigation.
Shangri-la resort, famous for its ancient wooden structures and cultural relics, was destroyed in the fire on January 11, and also forced the evacuation of 2,600 people.
While more than 240 houses were damaged, another 43 had to be dismantled. The blaze lasted about ten hours.
Apart from the houses, shops and infrastructure facilities, the fire damaged cultural relics, Tibetan thangka and other Tibetan art.
Dukezong is one of the most renowned resorts in Shangri-la, known for its well-preserved ancient Tibetan dwellings.