Mei Xiang, the female giant panda at the Smithsonian's National Zoo in Washington, eats breakfast Dec. 19, 2011. Zoo officials say rising hormone levels indicate she may be pregnant. (Susan Walsh/AP)

Attention, panda fans: Mei Xiang, the National Zoo’s female giant panda, may be pregnant.

Zoo officials announced Friday morning that Mei Xiang had experienced a secondary rise in urinary progesterone. In other words, her hormones are rising in a way that might suggest a pregnancy.

It will take 40 to 50 days to know for sure, and even then, the only conclusive evidence will be if Mei Xiang produces an actual panda cub, zoo officials said.

The news comes less than a year after Mei Xiang lost a cub, the sad culmination of a series of attempts by zoo officials to impregnate her. Mei Xiang had five consecutive false pregnancies between 2007 and 2012. Last year, she became pregnant and successfully gave birth, but the week-old cub died due to liver abnormalities and fluid in the abdomen.

Officials said in a news release that Mei Xiang was artificially inseminated twice on March 30 after natural breeding attempts with the zoo’s resident male panda, Tian Tian, were unsuccessful.

During the first procedure, she was inseminated with fresh sperm from Tian Tian and frozen samples that were collected in 2003. In the second procedure, Mei Xiang was inseminated with Tian Tian’s frozen 2003 sperm as well as frozen sperm from the San Diego Zoo’s male giant panda, Gao Gao.

Ever since, the National Zoo’s “panda team” has monitored Mei Xiang’s hormones. Veterinarians will continue to conduct daily hormone analyses as well as ultrasounds as often as Mei Xiang “chooses to participate in them.”

Officials noted that giant panda fetuses don’t start developing until the final weeks of gestation, making it difficult to determine whether there is a pregnancy. As a result, panda watchers will rely on hormone analysis and behavioral changes as indicators.

Mei Xiang has started to build a nest, which is consistent with the hormonal changes she is experiencing and could be a sign that she is preparing for a baby.

Zoo officials will eventually close off the portion of the panda habitat nearest to Mei Xiang’s pen to “provide extra quiet” for the possible mom-to-be.