Beijing: Chinese authorities are demanding exemplary punishment for an American man who allegedly stole a terracotta warrior’s thumb while it was on show at a Philadelphia museum.

According to reports in US and Chinese media, Michael Rohana, 24, was attending a pre-Christmas party at the Franklin Institute when he went through an unlocked door into the Terracotta Warriors of the First Emperor exhibition.

Using his smartphone as a torch, Rohana allegedly entered the exhibition at about 9.15pm on 21 December, embraced one of the ancient sculptures, and took a selfie before appearing to snap off a chunk of its left hand and pocket it.

Museum staff did not notice the absent digit until 8 January. Five days later, having tracked down the suspect through surveillance footage and credit card transactions, investigators went to Rohana’s home. “Rohana admitted ... he had stashed the thumb in his desk drawer,” China’s official news agency Xinhua reported .

USA Today said a friend of Rohana had seen a photo of the missing thumb on Snapchat. Rohana was arrested, charged with concealment of a major artwork and bailed after surrendering his passport.

On Monday, Wu Haiyun, that head of the group that loans the terracotta army to overseas museums, told Chinese television a “serious protest” had been lodged. “We ask that the US severely punish the perpetrator,” Wu added .

According to the South China Morning Post , another official said: “The terracotta warriors are national treasures ... We express strong resentment and condemnation towards this theft and the destruction of our heritage.”

Xinhua identified the affected warrior, one of 10 loaned to the Philadelphia museum, as a 2,000-year-old sculpture called Cavalryman. He is one member of the terracotta army, an 8,000-strong earthenware force commissioned to be buried alongside, and guard the tomb of, China’s first emperor, Qin Shi Huang. The sculptures were unearthed in 1974 and have become one of China’s biggest tourist attractions.