Chinese state media say a heater left unattended caused a fire that destroyed an ancient Tibetan town in southern China's Yunnan province.

The official Xinhua News Agency said late Friday that authorities detained Tang Ying, operator of the Ruyi Inn guesthouse in the old neighborhood of Dukezong in Shangri-La county.

Xinhua said Tang was under investigation for allegedly causing the Jan. 11 fire that burned for nearly 10 hours, destroying 343 houses and many historic artifacts.

It said Tang forgot to turn off the heater, which later set fire to a curtain.

Local authorities have said a million-dollar fire prevention system failed to prevent the blaze. Witnesses say hydrants failed to pump out water and that fire engines were kept outside the area's narrow alleys.