BEIJING — A fire prevention system costing more than $1 million wasn’t functioning and failed to prevent a blaze that razed an ancient tourist town in southwest China, the fire service said Monday.

The system in Dukezong had been shut down to prevent pipes from bursting in the below-freezing temperatures, the Deqen prefecture fire brigade said on its microblog.

In addition, the freezing temperatures lowered water pressure in hydrants when the fire broke out at about 1:30 a.m. Saturday. The wooden houses burned quickly, while fire trucks were unable to penetrate narrow streets.

The official Xinhua News Agency said investigators had determined that the fire started at an inn when a faulty electrical outlet set a curtain on fire.

Tourism is virtually the only industry in the traditional Tibetan region. The ancient quarter of Dukezong dates back more than 1,000 years and is known for its cobbled streets, ancient structures and Tibetan culture.

The fire raged for nearly 10 hours and destroyed 242 structures. About 2,600 people were left homeless, although no casualties were reported.

The county surrounding Dukezong renamed itself Shangri-La in 2001, referencing the mythical Himalayan land described in James Hilton’s 1933 novel.