The Zhejiang provincial department of health has announced that the third man in China has died from the H7N9 virus. The disclosure of the third death comes only days after Chinese authorities announced the first three known cases of humans infected with the H7N9 bird flu virus on Sunday. The total number of people infected with H7N9 in China has risen to nine.

The death was a 38-year-old man who died on March 27 in his home province of Zhejiang in eastern China. He worked in nearby Jiangsu province, where at least four other cases of humans infected with H7N9 were reported Tuesday. Two other people who died — men aged 27 and 87 — lived in nearby Shanghai. The World Health Organization confirmed those deaths Monday.

Chinese authorities are trying to find the source of the human infections. They have so far said there are no signs of transmission of the H7N9 virus between any of the victims or people they have come into close contact with, suggesting the virus isn’t highly contagious among humans.

They have also dismissed suggestions linking the infections with the discovery of thousands of pig carcasses from the Huangpu River which runs through Shanghai. The Shanghai Animal Disease Prevention and Control Center on Monday tested 34 samples of pig carcasses pulled from the river and found no bird flu viruses.

The World Health Organization said Monday it was “in contact with the national authorities and is following the event closely.”