LANZHOU, July 24 -- Yumen City in northwest China's Gansu Province on Thursday lifted a nine-day quarantine on an area in which plague caused one death.

A total of 151 people who had close contact with the infected man had been put in quarantine and under medical observation. None of them has reported symptoms of the disease, according to a report submitted by the local authorities and approved by the provincial government.

Plague is categorized as a Class A infectious disease, the most serious under China's Law on the Prevention and Treatment of Infectious Diseases.

A 38-year-old man in Yumen died of plague on July 16. He had been in contact with a dead marmot, a member of the squirrel family.

During the quarantine, local authorities aided with disease prevention, and control specialists sent by the National Health and Family Planning Commission carried out disinfection and rat extermination and educated locals on how to guard against plague.

The experts said plague is currently in a communicable, "active" phase among the local rat population.