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The man died in Yumen city, Gansu province, on 16 July.
A total of 151 people have been placed under observation, Xinhua news agency says. Authorities have isolated a part of the city centre and three sections of Chijin town which is an hour away.
The man was believed to have caught the infection after contact with a marmot.
Marmots are large, squirrel-type rodents that live in mountainous areas.
The victim is reported to be a 38-year-old man who had fed a dead marmot to his dog.
The deputy head of the hospital where the man died told reporters that the victim had arrived with an increased heart-rate and seemed to be slipping into shock. The hospital has since been quarantined.
It is not clear from reports how big the four quarantine zones are. Ten checkpoints have been set up around Yumen and Chijin.
Those in quarantine all had contact with the man, Xinhua said. None was showing signs of infection, it said.
Officials have told reporters that the group could be released after nine days of quarantine if no further cases of plague appeared among them.
Yumen is a small city in western Gansu province, which borders Xinjiang. The last reported case of bubonic plague in the city was in 1977, Xinhua said.