The female giant panda at Edinburgh Zoo is showing encouraging signs she may be pregnant, according to keepers.
There are indications Tian Tian could give birth to the UK's first panda cub within weeks, zoo staff say.
Changes in the levels of the panda's protein and her progesterone hormone suggest her artificial insemination in April was successful.
Keepers have also noted behavioural changes such as a lack of appetite, restlessness and nesting behaviour like making a bed of straw.
Experts are being cautious as it has not been possible to carry out an ultrasound and the signs may also be symptoms of a pseudo-pregnancy.
Iain Valentine, director of the zoo's panda project, told BBC Good Morning Scotland that the signs are "hugely exciting" because a panda has never been born in the UK. Since the artificial insemination, which took place in April, we've been monitoring hormones and we've also been monitoring an acute protein in her urine. So we've got to a point where the profile that she has been building up over the last few months is looking quite promising."
A second rise in progesterone hormone levels was detected in Tian Tian on July 15 and confirmed on Wednesday, according to the Royal Zoological Society of Scotland (RZSS), the conservation charity that owns Edinburgh Zoo. RZSS has been working with international experts to determine whether Tian Tian is expecting a cub.
The cub, or cubs, would be named 100 days after birth, in keeping with Chinese tradition, and would officially be the property of China. Confirmation of the baby panda's sex is likely to be by physical examination at around one to three months old.
Tian Tian and the zoo's male, Yang Guang, are the UK's only pair of giant pandas. Keepers hoped that the pair would mate naturally but that was not attempted as scientists decided that Tian Tian showed signs not ''conducive to mating''. Tian Tian was also inseminated with frozen semen from another panda called Bao Bao who lived at Berlin Zoo. Conservation geneticists will use blood samples from any cub to establish who is the father. If twins are born, they could have different parentage.
The pandas arrived from China in December 2011 and have been a popular attraction, with visits from around 500,000 people in their first year, including actor Nicole Kidman and the Princess Royal.