Chinese authorities have found traces of a new bird flu virus that has killed six people in more areas in Shanghai, state media reported.
Authorities have slaughtered over 20,000 birds at a large poultry market in the city.
State-run Xinhua news agency said samples of the H7N9 virus were found at two markets selling agricultural products in the Minhang district of Shanghai, a city of 23 million people that is China's financial hub.
The markets were near the Huhuai live poultry market where infected pigeons were discovered earlier in the week and where the culling was carried out.
The new strain of bird flu has infected 16 people in China, all in the east of the country.
Six people have died, and the outbreak has spread concern overseas and sparked a sell-off in airline shares in Europe and Hong Kong.
The strain does not appear to be transmitted from human to human, but authorities in mainland China and Hong Kong said they were taking extra precautions.
Shanghai has banned all live poultry from other parts of the country from entering the city, and has now closed three markets to stem the spread of the virus.
Hong Kong's government said it is intensifying surveillance of travellers and poultry coming into the city.
China and Hong Kong were badly hit by the 2002-2003 epidemic of Severe Acute Respiratory Syndrome (SARS) that started in China and killed about 10% of the 8,000 people it infected worldwide.