BEIJING - Construction companies in Beijing will need to keep a close eye on emissions of dust and other forms of pollution at their existing construction sites if they want to bid on new projects, a city government official said Tuesday.

It was announced at a Tuesday "green construction" conference that Beijing authorities will ban construction companies from submitting bids for new projects for a period of six months if their existing projects are found to have "irregularities," including large amounts of dust emissions and spilled construction materials.

Chen Gang, deputy mayor of Beijing, said city government officials will conduct random inspections of 100 construction sites next week, adding that county- and district-level officials will be conducting examinations as well.

"Construction in Beijing has reached a scale not seen since the 2008 Olympic Games. We have more than 10,000 construction sites at the moment, so we need to pay close attention to dust pollution," Chen said.

The city's safety and quality supervision department of Beijing inspected 225 construction sites in early April, suspending construction at eight of them.

In 2011, the city's housing and urban-rural development commission and environmental protection bureau ordered construction companies to equip their sites with wheel-washing equipment to reduce dust emissions from vehicles.