The worst air pollution to hit Shanghai this fall will continue to ease, the city's environmental authorities said on Friday.

The financial hub had been enveloped in heavy smog since Thursday, forcing the Environmental Protection Bureau to launch an emergency plan and ban large-scale outdoor activities and sports events from 7 am on Friday.

According to the Shanghai Environmental Monitoring Center, the city's air quality index hovered at 251, indicating serious pollution, at 9 am on Friday. But conditions started to improve and by 1 pm on Friday, the PM2.5 level had fallen to 55.5 micrograms per cubic meter.

The center said the air quality will continue to improve on Saturday.