PHOENIX (AP) -- Marchers carrying signs, banners and flags from the United States and Mexico filled central Phoenix Saturday, protesting the state's tough new crackdown on illegal immigration.

Dozens of police officers lined the route, but said there were no arrests. Police declined to estimate the size of the crowd, but it appeared at least 10,000 to 20,000 protesters turned out. Organizers had said they expected the demonstration to bring as many as 50,000 people.

With temperatures in the 90s, Phoenix police say about 20 people were treated for heat or fatigue-related symptoms, and seven of them were taken to a hospital.

The law's opponents also gathered elsewhere, including the Texas Capitol in Austin and outside the U.S. Embassy in Mexico City.