Edinburgh Zoo said Tian Tian has started to produce colostrum and is still being monitored by experts.
It is "really difficult" to tell if a panda is pregnant, the zoo said in a statement.
Tian Tian has kept her keepers and the public guessing since she was artificially inseminated in April.
In August, Edinburgh Zoo said she was showing encouraging signs of pregnancy and she was later placed on 24-hour surveillance, with hopes that she could give birth in late August or September.
When that did not materialise, the zoo cautioned that any birth could happen two weeks later than thought. Edinburgh Zoo said it is still possible Tian Tian is expecting and they will continue to prepare for a new arrival.
Meanwhile, the zoo said that male panda Yang Guang was recently removed from display due to illness. It is believed he has a metabolic disorder but should recover in a couple of weeks.