The death of a giant panda at a zoo in the southeastern United States was caused by heart disease, according to an autopsy by Chinese and American scientists. The experts said the preliminary autopsy findings, released on Sunday, would be confirmed by further pathology tests. Le Le, who died on February 1 at Memphis Zoo in the state of Tennessee, was set to return to China after the end of a 20-year loan agreement . The Chinese Association of Zoological Gardens said China was prepared for Ya Ya, another panda at the zoo, to return home. “The Chinese and American sides are liaising … so that Ya Ya can be transported back to China as soon as possible,” the association said on Sunday, adding that Chinese authorities had issued import and quarantine permits and confirmed a quarantine site for her. After examining Ya Ya at the zoo and reviewing her medical reports, the Chinese experts said she suffered from hair loss caused by skin disease but had a good appetite, normal stools and a stable weight . “The expert team discussed Ya Ya’s fur abnormalities with the Memphis Zoo. They have also put forward suggestions and requests to US counterparts about Ya Ya’s healthcare,” the association said. State-run The Beijing News on Thursday quoted the Beijing Zoo as saying it had prepared for Ya Ya’s return, which is set to take place on April 7 when her loan agreement expires. Le Le, whose name means “Happy Happy”, was born in 1998 and sent to the US zoo in 2003, along with Ya Ya. In December, the zoo said the duo would be sent back to China in early 2023 after the end of the loan agreement, a move celebrated on Chinese social media . Animal rights groups had claimed the zoo was mistreating the pandas. Memphis Zoo rejected the accusations and denied the return of the pandas was related to the claims. A spokesman for the zoo told Reuters the return was part of an agreement with China that required foreign zoos to allow the loaned pandas to spend their final days on Chinese soil. After Le Le’s sudden death, China sent experts to the zoo to investigate the cause with American peers. According to the Chinese association, the joint autopsy ruled out common causes of accidental deaths in animals, including aortic rupture, liver abscess rupture, serious blood loss and volvulus – an abnormal twisting of the intestine that can cause bowel obstruction. Panda diplomacy: the latest chapter for a safe space in US-China relations For decades, China has sent pandas overseas as a diplomatic tool to strengthen ties. In 1972, after US president Richard Nixon met Chinese leader Mao Zedong , China gave pandas Ling Ling and Xing Xing to the United States. Most pandas go to developed countries with geopolitical clout that can pay the panda leasing fees of up to US$1 million annually and cover the cost of their special enclosures and diet. The top panda recipients in 2019 – the US with 11, Japan with nine and South Korea with four – were also among China’s biggest trading partners.