Health authorities in Beijing said on Thursday that one of the two patients who were recently diagnosed with a severe and infectious form of plague was "in critical condition but the patient's health had not deteriorated."

The other patient was now in stable condition, the Beijing Health Commission said.

The commission added that as of early Thursday morning, it had not detected signs of infection among people who had come in contact with the patients.

The two infected people came from XilinGol League, the Inner Mongolia autonomous region, and arrived in a hospital in Beijing this week to seek treatment. They were confirmed by the Chinese Center for Disease Control and Prevention on Tuesday to have contracted with pneumonic plague.

The center added that the possibility of a wide epidemic was extremely low.

Health and emergency management authorities in XilinGol League said a series of measures have been imposed to prevent further spread of the disease, including tracking those suspected of exposure to the patients, enhancing monitoring around the neighborhoods of their residency and stepping up education over the awareness of the plague among local medical workers as well as the public, XilinGol Daily, a local newspaper in XilinGol League, reported on Wednesday.

Fan Mengguang, a senior official with Inner Mongolia's CDC center, was quoted by the newspaper as saying that experts were looking into the cause of the plague and the spread of the disease was under control.

Plague is considered one of the most dangerous infectious diseases by health authorities in China. Symptoms include fever, severe toxemia, swelling of lymph nodes, pneumonia and bleeding tendency.

It is best known for causing the Black Death in the 14th century, which killed more than 50 million people.