Efforts to artificially impregnate a giant panda on loan from Mexico have failed, officials at Tokyo's Ueno Zoo said Wednesday.

Shuan Shuan, a 17-year-old female panda, underwent artificial insemination in February after attempts to naturally mate her with male panda Ling Ling, 18, proved fruitless.

Of the nine giant pandas currently kept in Japan, Ling Ling is the only one Japan owns. The others are all on loan from other countries. Ueno Zoo has been trying to gain a panda cub so the nation will continue to have its own pandas.

The zoo has not seen a panda birth in 16 years.

Officials said it would discuss what future course of action to take concerning Shuan Shuan with their counterparts from Chapultepec Zoo in Mexico City, which owns her. They added that they would like to try artificial insemination again. The initial agreement between the two institutions was that Shuan Shuan would be returned in August.

Shuan Shuan came to Japan in December. After the artificial impregnation process, she showed signs of pregnancy, including a loss of appetite and moves indicating she was preparing a nest.

However, her appetite began to grow again toward the latter half of June, and there have been no other indications of pregnancy, zoo officials said.