MEXICO CITY (AP) — Thousands of school-skipping "tween" girls and their parents streamed into Mexico City's historic main plaza on Monday, hoping to get the best spots for a free concert hours later by teen superstar Justin Bieber that is expected to draw 200,000 people.

The gray and reddish stones of the plaza were covered in a sea of purple as the mainly 10 to 14-year-old crowd paid homage to what is reported to be Bieber's favorite color.

Under a hot sun, girls trundled through security checkpoints with hats and umbrellas, staking claim to some of the roughly 80,000 spots allocated in the plaza itself. Another 120,000 or more are expected to watch on giant screens erected on nearby streets.