China has arrested a museum official for stealing some of the precious antiquities he was supposed to be guarding. It is the biggest such theft reported in half a century of Communist rule.

Li Haitao was supposed to be supervising security at a museum in Chengde, a city north of Beijing that was once a summer resort for the emperor's court.

Mr. Li is accused of stealing 158 relics during 12 years, substituting fake artifacts or doctoring inventories to conceal his crimes.

Seventy relics were found in Mr. Li's home and officials say they expect to quickly track down 40 more that were sold.

A mainland Chinese antiquities expert raised the alarm when he found two relics labeled "Forbidden City" at an auction last October in Hong Kong.

The Forbidden City, in the heart of Beijing, is the elaborate walled palace that was home to China's emperors for centuries.

Officials say some of the stolen artifacts were "first-class" antiquities because of they have major historical or artistic value.

Historian Chen Jun Qi, a relics expert who works at the Forbidden City Museum says this incident has taught a painful lesson to museums across the nation.

Mr. Chen says the incident highlights flaws in the way institutions care for the symbols of China's 5,000-year heritage. He says some changes are in order.

Chinese officials have not said exactly what charges Mr. Li will face. Chinese law allows the death penalty in some extreme cases of relic theft.