Mexico City has discontinued a pollution alert after three days of persistently high smog levels and will allow more cars on the streets Friday.

Smog remained at almost 1.3 times acceptable limits Thursday, but authorities said winds were expected to pick up and help clean the air.

During the three-day alert, 40 percent of cars were ordered off the street each day.

Under a rule in effect through June, one-fifth of the city's vehicles normally must stay at home on a weekday, with the day determined by license plate numbers.

Before the rule was implemented last month, newer or cleaner cars were exempt from the one-day driving ban.

The pollution spike is due to seasonal weather patterns and the increasing number of cars in the city.