LANZHOU -- Two snow leopards roamed into the working area of a hydropower station in Northwest China's Gansu Province, according to the station on Monday.

The station, which belongs to the Longyang Hydropower Co., Ltd in Sunan Yugur Autonomous County, is located in the Qilian mountains. Surveillance camera footage showed a dark shadow wandering outside the gate of the station at 6 a.m. on Nov. 18 before worming in from under the door, followed soon by another one.

"Then we adjusted the camera and the images of two snow leopards moving in the working area of the station were clearly presented," said Chen Haiyang, a staffer with the station.

"I thought they were foxes at first, but as the camera zoomed in, I realized they were snow leopards," Chen said. "Wild animals like blue sheep frequented before but this is the first time the big cats were found here. I was very scared, after all, they were visiting a workplace."

"A range map of the snow leopards shows a sign of expanding, but overall, it's uncommon for the mammal to appear in areas of human activity," said Ma Duifang, an official with the administration of the Gansu section of the Qilian Mountains National Park, which covers 50,200 square km in Gansu and Qinghai.

"When encountering snow leopards, one should keep a safe distance and avoid making provocative or threatening actions," Ma said.

"Wild animals, including snow leopards, have appeared frequently in recent years, which indicates their habitats are constantly improving," said the expert who has been engaging in wildlife research in the mountains for more than a decade.

Snow leopards are under China's highest national-level protection and are listed as vulnerable by the International Union for Conservation of Nature. The species mainly inhabit the Himalayas in central and southern Asia at an altitude of 2,500 to 4,500 meters.

In China, they are found in the alpine areas in southwestern and northwestern regions including Tibet, Sichuan, Xinjiang, Gansu and Inner Mongolia.