MEXICO CITY, Sha'ban 18, 1437, May 25, 2016, SPA -- Mexico City officials issued their sixth pollution alert of the year, requiring more cars to stay off the roads Wednesday to reduce emissions, according to AP. The alert automatically doubled from 20 percent to 40 percent the proportion of vehicles not allowed to circulate on a weekday. It was declared Tuesday afternoon after ozone levels rose above 150 percent of acceptable limits. The alert also comes with other measures such as restricted activity at some gas stations and factories and a ban on burning solid or liquid materials. Mexico City issued its first pollution alert in over a decade in March. Normally one-fifth of the vehicles in the city and surrounding suburbs must stay at home on a weekday, determined by license plate numbers. The pollution spike is due to seasonal weather patterns and the increasing number of cars in the city. --SPA 02:03 LOCAL TIME 23:03 GMT www.spa.gov.sa/w