A panda that died suddenly last Thursday night was killed by gas poisoning in a zoo in Jinan City of east China's Shandong Province, zoo management said Monday.

Press conference held by zoo management.

Initial investigations showed that the panda died after inhaling gas disinfectant from a nearby former air-raid shelter. The gas was composed of chlorine, chlorine hydride and carbon monoxide, said Liu Jungang, deputy Party secretary of Jinan Zoo.

Workers were disinfecting the air-raid shelter when the gas leaked to the zoo's panda house through an air-pipe.

Police are investigating the case.

The panda was found poisoned at around 7 p.m. and died in a local hospital after three hours of treatment failed.

The female panda Quan Quan, a star at Jinan Zoo and a "heroic mother," had given birth to seven cubs.

Quan Quan arrived at Jinan zoo three years ago. Aged 21, the panda was the equivalent of a woman more than 70 years old.

Giant pandas are among the most endangered species in the world, with only a few thousand living in the wild, mountainous areas of southwest China.