One bubonic plague case has been confirmed in Inner Mongolia, local health authorities said on Sunday, though it is unrelated to the previous two cases diagnosed in Beijing on Tuesday, which were pneumonic.

The newly-diagnosed patient, a 55-year-old worker from a quarry in Inner Mongolia's Xilin Gol League, complained of persistent fever at a county-level hospital and is now confirmed as carrying the bubonic form of plague mainly infecting the lymph nodes, according to a statement released by the health commission of Inner Mongolia.

He is now being quarantined and under treatment at the hospital, and 28 close contacts have also been quarantined for medical observations. None have displayed symptoms as of Sunday afternoon, the commission said.

According to the commission, the patient skinned and ate a wild rabbit on Nov 5 at the quarry.

Fan Mengguang, deputy director of Inner Mongolia's disease prevention and control center, said the new case is "isolated and unrelated" to the two patients diagnosed with plague in Beijing on Tuesday.

The two patients also came from Xilin Gol league, but they were diagnosed with pneumonic plague, a different form that mainly infects the lungs and is more damaging than the bubonic type.

People who came into contact with the two patients have shown no symptoms as of Sunday afternoon, the commission said in the statement.