BEIJING (AP) — Chinese authorities have lifted a nine-day quarantine in parts of a northern city that was imposed after a man died of bubonic plague.

A total of 151 people were under observation in the city of Yumen in Gansu province. Authorities determined they had come in contact with a man who died of the plague July 16. State-run Xinhua News Agency quoted a report by local authorities Thursday as saying that none of them had symptoms of the disease.

According to Xinhua, investigators believe the 38-year-old man contracted the bacterial infection after contact with a marmot.

Authorities in the city of about 180,000 have carried out disinfection and rat extermination during the quarantine.

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