BEIJING -- An analysis of the sources of air pollution in Beijing, Tianjin and Shijiazhuang will be finished by the end of June, an official with China's environmental authority said on Sunday.

The environmental authorities are working with the Chinese Academy of Sciences and the Chinese Academy of Engineering to conduct the research and will jointly release reports on the results in the research, said Zhao Yingmin, director of the pollution control and management department of the Ministry of Environmental Protection.

Zhao made the remarks when giving a report on air pollution in China to the Environment and Resources Protection Committee of the National People's Congress, China's top legislature.

The analysis of the sources of air pollution in Beijing has already been finished and published earlier this month and the result revealed that about 64 percent to 72 percent of the air pollutants in Beijing are locally generated, Zhao said.

The official said the yearly average density of fine particular matter, or PM2.5, in Beijing last year was 89.5 micrograms per cubic meter, far beyond the pollution control cap target of 60.