China announced Thursday a raft of emergency measures it would take if skies don't clear up further for the Olympic Games, including more factory shutdowns and further restrictions on cars.

The polluted air, one of the biggest worries for Olympic organizers, prompted Beijing to begin drastic measures earlier this month, including pulling half the city's 3.3 million vehicles off the roads, halting most construction and closing some factories in the capital and surrounding provinces.

The emergency measures include shutting another 200-plus factories and further restricting vehicles across Beijing, Tianjin city and surrounding Hebei province, according to a public notice posted Thursday on the government's Web site.

In the capital, an additional 105 machinery, chemical and construction materials factories would be shut temporarily. In Tianjin, 80 miles east, 56 factories would be closed, while 61 factories would be shut in Hebei.

In Beijing, besides current restrictions banning odd/even license plates on alternate days, automobiles whose last two digits on its plate matching the date would be banned. Tianjin and Hebei would begin implementing similar odd/even restrictions.

In addition, all construction sites across Beijing would be halted.

The notice said once the games begin Aug. 8, the contingency measures would kick in if authorities decide the air quality had not improved enough.

"If there are unfavorable weather conditions, and the air quality is forecast to not to meet the standards in the following 48 hours, the operating commanding center would suggest the contingency plans be initiated," it said.

On Wednesday, the city's air pollution index dropped to 44, less than half what it was a day earlier, and the lowest since July 20 when the first measures came into effect.

A cooling wind and some rain earlier this week helped sweep away pollutants and gave Beijingers a respite from the sultry heat and humidity that had cloaked the city for days.

The measures are having the desired effect, Du Shaozhong, deputy director of Beijing's Environmental Protection Bureau, told The Associated Press in an interview.

"The daily data since July 20 shows an improvement in air quality. It reflects the results since we restricted traffic and stopped heavy-polluting factories and construction," he said. "That's why we say the measures have been effective."

A reading below 50 is considered good and between 51 to 100 is moderate. But critics say even moderate levels are still above the World Health Organization's guidelines for healthy air.

Some experts argue that the recent weather conditions, not the curbs, were largely responsible for the cleaner air.

Athletes participating in the Aug. 8-24 games have raised concerns about the impact of the city's pollution on their health and their performance from the start. Some of the 10,500 Olympic athletes began arriving in large numbers this week — though others headed to train in neighboring South Korea, Japan and other places to avoid Beijing's air for as long as possible.