China's agricultural authorities said Thursday the infectious H7N9 avian flu virus has been detected from pigeon samples collected at a marketplace in Shanghai, as the country reported its fourth death from H7N9 infection.

The samples were collected at a marketplace selling agricultural products in the Songjiang District of Shanghai and tested H7N9 positive by the national avian flu reference laboratory, according to a statement by the Ministry of Agriculture.

After gene sequence analysis, the national avian flu reference laboratory concluded that the strain of the H7N9 virus found on pigeons was highly congenetic with those found on persons infected with H7N9 virus.

The ministry has ordered beefed-up monitoring of H7N9 bird flu virus in more areas.

Also on Thursday, three more suspected H7N9 cases were reported in Shanghai, where three H7N9 human infection cases have been confirmed.

China has thus far confirmed 11 human cases of H7N9 infections.

China's health authorities have promised transparency and cooperation to the World Health Organization (WHO) in regards to human infections of the new strain of bird flu.

The Chinese Center for Disease Control and Prevention said Wednesday that no human-to-human transmission of H7N9 has been discovered and no epidemiological connection between these cases has been found. Endi