The Franklin Institute, a museum in the US state of Pennsylvania, pledged on Friday to protect a set of China's terracotta warrior statues with the "utmost care and reverence," after a man stole a statue's thumb.

"The Franklin Institute has the utmost respect for the Terracotta Warriors and the rich Chinese cultural heritage they embody," the museum said in a statement obtained by Xinhua.

The statement came a week after authorities revealed that on Dec 21, a man stole a thumb of a Chinese terracotta warrior statue exhibited at the institute.

The thumb was retrieved by the FBI and the suspect, identified as 24-year-old Michael Rohana from state of Delaware, was arrested and released on bail. He faces charges of theft of a major artwork from a museum and other offenses.

The 10 terracotta warrior statues at the Franklin Institute in Philadelphia were on loan from China for a special exhibition that began in September 2017 and will run until March 4.

The statues date back to at least 209 BC For more than 2,000 years, the life-size statues guarded the tomb of China's first emperor Qin Shi Huang, which covers an area of 56 sq km in Shaanxi province in northwestern China.

While describing the theft as a "deplorable act," the institute said that it has been working with the FBI and other authorities to ensure that "justice for the individual responsible is served."