China has demanded an American be "severely punished" after he was alleged to have stolen a thumb from a terracotta warrior while it was on display in the United States.
Authorities also want compensation for the US$4.5 million ($6.1m) exhibit, which was on display at the Franklin Institute in Philadelphia.
Reports said that Michael Rohana, 24, from Delaware, attended a party at the institute on December 21 on his way into the special exhibit, Terracotta Warriors of the First Emperor.
China's Xinhua news agency, citing the FBI, said Rohana "used a cellular telephone as a flashlight, looked at various exhibits displayed in the then-closed showroom, stepped up on to a platform supporting one of the statues, and took a selfie with it".
"Rohana, according to the affidavit, put his hand on the left hand of the statue, appeared to break something off from the Calvaryman's left hand and put it in his pocket, and then left."
Shaanxi Cultural Heritage Promotion Centre, which arranged the loan of 10 of the statues, "strongly condemned" the theft.
An official urged the US authorities to "seriously investigate" the incident, to "punish severely the culprit" and launch "compensation procedures".
The statues are among 8000 soldiers, chariots and horses unearthed in 1974 in Xian, China. The terracotta army guards the burial site of Qin Shi Huang, China's first emperor.