The second-straight day of smog led to the cancellation of all flights at Taiping International Airport, China's Xinhua News Agency reported.
The pollution led to visibility of less than 164 feet in downtown Harbin, a metropolitan area of about 10.6 million people that is the capital of Heilongjiang province, the state-run news agency said.
In addition to the airport closure, all elementary and middle school classes were canceled and some public buses stopped running.
Meteorologists forecast the smog would continue Tuesday.
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