Veterinarians at the National Zoo artificially inseminated its female giant panda Mei Xiang on Saturday after natural mating failed to occur, zookeepers said.

Mei Xiang was put under general anesthesia and inseminated with a combination of fresh and frozen semen collected from the zoo's male giant panda, Tian Tian.

The Washington zoo said scientists performed a second and final insemination later on Saturday evening.

"It will be several months before we know if she is pregnant," the zoo said in a tweet.

Animal keepers detected a rise in panda hormone levels and breeding behaviors last week. A team of scientists performed the artificial insemination after keepers determined there had been no natural mating overnight between the two pandas.

Veterinarian Tang Chunxiang traveled from China's Conservation and Research Center for the Giant Panda in Sichuan province to assist.

Dave Wildt, head of the Center for Species Survival at the Smithsonian Conservation Biology Institute, said, "We are hopeful that our breeding efforts will be successful this year, and we're encouraged by all the behaviors and hormonal data we've seen so far."

Scientists will continue to monitor Mei Xiang's hormone levels in coming months and conduct ultrasound tests to determine whether she is pregnant. A pregnancy lasts between 95 and 160 days, they said.

Mei Xiang has given birth to two cubs. One died a week after its birth last year. The other, Tai Shan, was born in 2005 and is now at the China Conservation and Research Center for the Giant Panda in Wolong, Sichuan province.

The panda house at the zoo has been closed since Tuesday but was scheduled to reopen on Sunday.

Reuters-AP