Egyptian authorities have issued an international alert for the return of a priceless statuette of Tutankhamun’s sister, which was stolen from a museum over the summer.

According to the Telegraph, the carved limestone figurine of “A Daughter of the Pharaoh Akhenaten,” created during the 14th century B.C., went missing from Mallawi City Museum in August during days of violent skirmishes between police and Islamists as a result of the ousting of President Mohamed Morsi.

As the Telegraph reports, the figurine was the prize exhibit of the museum, and was due to be transferred to a new facility still being built to honor the family of Akhenaten. Officials think looters used the rioting to steal roughly 1,000 pieces from the museum, including the statuette of Tutankhamun’s sister.

"I think the looters knew what they were taking," Egyptian archaeologist Monica Hanna said.

More than 600 pieces have been returned or seized by police, but around 400 artifacts, including a collection of Greek cold coins and multiple exhibits from the Akhenaten gallery, have still not been found, the Telegraph said.

According to the Telegraph, the situation deteriorated after Morsi was removed from power and pro-Muslim Brotherhood protests broke out across Egypt. "We heard what had happened in Cairo and started to see the gangs gather," said Jaihan Nessim, a curator at Mallawi Museum. "Then there were big crowds, and they started firing into the air."

The museum was closed and the tourist police assigned to protect the facility were driven off within hours. After that, looting commenced and the museum was virtually destroyed.

As the Telegraph notes, Hanna arrived three days later to find two teenagers ransacking the museum. "They said, ‘The government is destroying their people, so we are destroying this because it belongs to the government,’" Hanna said.

Col. Abdulsamie Farghali, the provincial chief of tourist police, has alerted the United Nations Educational, Scientific and Cultural Organization, as well as Interpol, about the missing figurine. According to the Telegraph, the fear is that the statuette of Tutankhamun’s sister would be smuggled out of the country and sold on the black market.

"I hope she is not," Hanna said. "It is a masterpiece. It was the highlight of the museum, and even though there were other highlights people went there to see the daughter of Akhenaten."

“I firmly condemn the attacks against the cultural institutions of the country and the looting of its cultural property,” Irina Bokova, director-general of Unesco, said in a statement. “This constitutes irreversible damage to the history and identity of the Egyptian people.”