The thumb of a nearly 2,000-year-old terracotta warrior was stolen while on display at the Franklin Institute. [Photo provided to China Daily]

A 24-year-old man has been charged with theft of a major artwork from a Philadelphia museum -- stealing a thumb from a Terracotta Warrior statue that is part of an exhibit on loan from China at the Franklin Institute, according to law enforcement authorities.

Michael Rohana took a selfie with the statue before allegedly snapping off the part at an after-hours party at the museum, authorities said.

The thumb was recovered at Rohana's home five days after it was taken and returned to the museum, authorities said.

Rohana has been charged with theft of a major artwork from a museum, concealment of major artwork stolen from a museum, and interstate transportation of stolen property, according to an affidavit filed on Friday in federal court. He was released on bail.

The director of the Shannxi Cultural Heritage Promotion Center was "shocked and enraged" by the incident, according to a statement it issued, and criticized the Franklin Institute for not notifying it quickly about the incident.

The Franklin Institute extended its apology to the center for security loopholes, according to the statement.

The Center also said it was seeking initiation of a compensation procedure.

The stolen thumb was found broken when this Terracotta Warrior was excavated, but the fracture had been repaired before the statue went on exhibition in the US, the center said, and the missing thumb was snapped from the exact repaired place.

Rohana was a guest at an Ugly Sweater party at the museum in December when he went into a closed exhibit of terracotta statues, according to law enforcement authorities.

The thumb came from the life-size clay soldier known as "The Cavalryman", part of the exhibit at the Franklin Institute on display through March 4.

The soldier is part of a "Terracotta Army" that provided after-life security at the burial complex of China's first emperor, Qin Shi Huang. The statues date from around 209 B.C. The exhibit contains 10 statues, including a general, a charioteer and a saddled horse.

The man walked into the darkened exhibit during a Dec 21 "Science After Hours" party, according to an affidavit by the FBI, USA Today reported. A door to the exhibit was closed, but apparently unlocked.

A surveillance video shows the guest alone with "a priceless part of China's cultural heritage," said FBI Special Agent Jacob Archer in an affidavit, according to the newspaper. Archer is a member of the FBI's Art Crime Team.

Archer's affidavit, filed Friday in federal court in Philadelphia, said Rohana of Bear, Delaware, entered the room briefly, then apparently invited two friends at the party for a private tour. Surveillance video shows the trio entered the exhibit at 9:15 pm.

The friends left the room, but Rohana allegedly lingered for a few minutes, using his cellphone as a flashlight to look at the figures, according to the affidavit.

At one point, he stepped onto a platform holding a warrior, "placed his arm around that sculpture and took a photograph of himself with the sculpture," Archer said.

Just before he left the room, Rohana "appeared to break something off the Cavalryman's left hand and put it in his left pocket," said the agent.

A museum staffer noted the finger's disappearance on Jan 8.

Surveillance video and credit-card information established that Rohana had attended the party with five friends from Delaware, authorities said.

One of the friends said she heard Rohana discussing the thumb on the ride home, according to the affidavit, part of a criminal complaint charging him with theft of major artwork from a museum and other offenses.

Another friend said Rohana posted a photo of "a finger" from a terracotta warrior on his Snapchat account one day after the party.

When Archer interviewed Rohana at his family's home on Jan 13, Rohana led the agent to his bedroom where the stolen thumb was in a desk drawer, according to the affidavit.

In a statement on Wednesday night, the Franklin Institute said "standard closing procedures were not followed" by a security contractor on the night of the party.

"As a result of this incident, we have thoroughly reviewed our security protocol and procedures and have taken appropriate action where needed," the institution said.

The facility also said security in place to ensure the safety of our artifacts" and noted an internal investigation gave the FBI "the information necessary to identify the suspect."

Hu Yumeng contributed to the story.