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Organizers of the March for Our Lives demonstration in Washington, D.C. claimed Sunday that some 850,000 people attended the pro-gun control event, but an imaging company said the turnout was much less.

Virginia-based Digital Design & Imaging Service Inc., which uses aerial photos to calculate crowd sizes, reported the event’s peak crowd size was at 202,796 people around 1 p.m., CBS News reported. The firm said the number's margin of error is 15 percent.

The January 2017 Women's March turnout in Washington, for comparison, was estimated at 440,000 people.

The National Park Service stopped providing crowd its own numbers.

Saturday's demonstration down Pennsylvania Avenue included students from Stoneman Douglas High School in Parkland, Fla., the site of the shooting massacre last month. The march was not allowed to be held on the National Mall because a "talent show" was being filmed, The Washington Post reported.

Many other cities outside of the nation's capital, including Portland, Boise, New York City, Chicago and Dallas, held their own marches calling for gun reform.

The Associated Press contributed to this report.