The baby giant panda at the Smithsonian's National Zoological Park was born with poorly developed lungs, which ultimately led to liver damage and then death, according to a statement released today by the zoo.

WATCH VIDEO: Watch as Mei Xiang and Tian Tian travel from China to the National Zoo.

This final necropsy puts to rest a slew of other theories purporting to explain how the infant died. One concern was that 217-pound mother Mei Xiang crushed her

female cub, who weighed a little less than 100 grams.

"There were no signs of external or internal trauma, so we

are certain that didn’t happen," Pierre Comizzoli, a reproductive specialist at

the National Zoo, told Discovery News. "The mother didn’t somehow squeeze the

cub to death."

BIG PIC: Baby Giant Panda Born at D.C. Zoo

An initial necropsy performed on September 23 showed that the week-old female cub had

fluid in her abdomen and her liver was hard in places.

According to the release issued today:

The final necropsy determined that lung and liver damage ultimately caused the cub’s death. Her lungs were poorly developed and likely caused her to have insufficient oxygen, which would be consistent with the changes in the liver. The mortality rate for pandas in their first year in captivity is estimated to be 26 percent for males and 20 percent for females. Some early mortality rates may be underestimated.

Zoo staff are now working with colleagues in China "to answer questions about

giant pandas that will ensure the best care in captivity and that will

help bolster the species’ numbers in the wild. The information about how

this cub died will add to the scientific body of knowledge about giant

pandas. The zoo will continue to work closely with its Chinese

colleagues and share the information it has learned about giant panda

reproduction and cub health."

As for the adult giant pandas Mei and Tian, the zoo says no decision has been made about their future. There's apparently an agreement with China that lasts through December 5, 2015. It stipulates that the zoo will continue to conduct research on breeding and cub behavior until then. Hard to do without a cub, but I was told that Mei is still young enough to give birth again.

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The mother is doing well and "is almost completely back to her old self." The zoo reports that her hormones have returned to normal levels, as has her

behavior. She's now going out in the mornings and spends most of her afternoons napping on her indoor rockwork.

She's eating well too, consuming "almost all of her bamboo and all of her leaf eater biscuits and produce."

The zoo also shares that they now have photos showing some of Mei's nesting. You can watch the time-lapse video made from the photos on the zoo's YouTube page.

(National Zoo photo of Mei)