Chinese health authorities said on Saturday they had discovered four more cases of pneumonia following an outbreak of what is believed to be a new coronavirus strain in the central city of Wuhan, raising concerns that the disease could spread further.

The four individuals were diagnosed with pneumonia on Thursday and are in stable condition, the Wuhan Municipal Health Commission said in a statement published shortly after midnight, a day after it confirmed the death of a second patient.

Nearly 50 people are known to have been infected and so far involve only individuals who have traveled to or live in Wuhan, but the World Health Organization (WHO) has warned that a wider outbreak is possible.