Officials in north China say the success of cutting emissions for the duration of the Asia-Pacific Economic Cooperation (APEC) meetings will prompt more measures to curb air pollution.

The promises were made as most polluting factories resumed production, which had been suspended or ordered to cut prodcution to ensure clean air during the APEC meetings in Beijing..

In Hebei Province, which neighbors Beijing, some factories might be permanently phased out, said Yin Guangping, vice head of the province's environmental protection department.

"Some factories affected by the suspension order were found to be unlicensed or illegal and they might not be allowed to reopen," Yin said, adding that the province was mulling "further measures" on air pollution control.

Nearly 4,000 factories were ordered to close or curb production in Hebei during the week-long APEC meetings that ended on Tuesday. The province relies heavily on its coal-fired steel plants and emissions from the area are partially blamed for the notorious smog that plagues Beijing.

To ensure clean air during the meetings, Beijing and its neighboring regions -- including Hebei, Tianjin, Shandong and Inner Mongolia -- imposed temporary restrictions, including halting emission-heavy production and limiting cars on the streets based on their license plates.

As a result, the Beijing sky remained blue during APEC despite predictions otherwise, with daily PM 2.5 density in the period falling to 43 micrograms per cubic meter, prompting Chinese netizens to coin the phrase "APEC Blue" to describe the clear sky.

But, with the lifting of the bans, Beijing reported light to medium air pollution on Saturday, with PM 2.5 density exceeding 200 micrograms per cubic meter in some parts of the city.

Inner Mongolia Autonomous Region, north of Beijing, promised to crackdown on construction sites and factories that violated pollution control rules in the wake of APEC, said Pan Yanzhao, vice head of the regions' environmental protection department.

"The APEC meetings have served to raise public awareness on the need to phase out excessive and outdated industrial capacity, so it presents a chance for us to place more pressure on heavy-polluting factories," said Ma Jinghua, vice head of Harqin Banner in Chifeng City, Inner Mongolia.