A blanket of humid air trapping smog brought Beijing's first pollution "red alert" on Tuesday although many residents ignored warnings to limit time outdoors and authorities said the pollution would last several more days. Hundreds of people, including toddlers, packed Tiananmen Square to watch a daily flag-raising ceremony while China's state radio said some motorists were ignoring a ban on vehicles bearing odd-numbered license plates. Rapid industrial growth and car ownership over the past decade or more have led to high levels of pollution in major urban areas and Chinese researches have identified the problem as a major source of unrest. Certain weather conditions can exacerbate the problem. Environment Minister Chen Jining called a special meeting late on Monday to urge greater vigilance against pollution in Beijing and nearby cities and he increased the number of environmental inspection teams to 12, ThePaper.cn, a state-backed news website, reported. Smog has been a public health concern in Beijing for years but the government's response has come under extra scrutiny in the past week because it faced heavy criticism for not issuing a red alert during an earlier episode of hazardous smog. A red alert means 30 percent of vehicles are ordered off the roads, heavy vehicles banned, schools advised to cancel classes, businesses recommended to allow flexible working hours and all "large-scale, outdoor activities" should be stopped. "This measure reflects that the government, at least, has the courage to face this problem," said Ma Jun, director of the Institute of Public and Environmental Affairs, a Chinese environmental group, referring to the red alert. "Before, they were more or less somewhat reluctant to acknowledge the problem. Now there's a willingness to face this problem directly." The red alert has been imposed until Thursday. Environmental group Greenpeace called it "a welcome sign of a different attitude from the Beijing government." Bernhard Schwartländer, the World Health Organization's representative in China, said the alert "means, first and foremost, that the Beijing authorities are taking air quality, and related health issues, very seriously." The Beijing City Emergency Office said "still weather, reduced cold temperatures and an increase in humidity" prompted the alert, the Xinhua state news agency reported. In the northern city of Taiyuan, six people were killed and four injured in a 33-vehicle pileup on a highway cloaked in smog, the Xinhua said. Some people in Beijing tried to dodge the restrictions. State media showed a policeman removing paper stuck over the last, odd, digit of a car's license plate. By late afternoon, the US embassy's monitoring station recorded "hazardous" air quality. Many city residents donned industrial-strength face masks. "I feel like I'm engaged in chemical warfare," one commuter said on social media. Still, the ruling Communist Party's official People's Daily, without a hint of irony, praised China's contribution to fighting climate change in a commentary written to coincide with climate talks in Paris. "People everywhere are looking forward to China's continuous progress on the road to green development, acting as a model for the world to tackle the challenge of climate change," the newspaper said.