Tucson, Arizona (CNN) -- Criminal defendants are expected to make initial appearances in federal courts in Phoenix and Tucson on Friday in connection with what one federal agency calls the largest human smuggling investigation in its history. U.S. and Mexican authorities arrested dozens of people Thursday in what U.S. officials say is "the culmination of a comprehensive year-long" investigation focusing on shuttle buses operating along the border between Arizona and Mexico. "This operation has dealt a serious blow to the infrastructure of some of Arizona's most prolific and profitable human smuggling organizations -- organizations that made their money by moving people," John Morton, homeland security assistant secretary for Immigration and Customs Enforcement, said at a news conference Thursday afternoon.
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Operation in Plain Sight deals "serious blow" to smugglers, Homeland Security official says
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Eight hundred agents and officers from nine agencies mobilized in Arizona
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Owners, employees of 5 Arizona shuttle services are among those taken into custody
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Saying U.S. sends "mixed messages," raids' timing draws ire of immigration group official
Plain Sight
The investigation is called @placeholder because of what officials call the "brazen nature" of the shuttle services, allegedly part of a confederation of illegal immigrant smuggling rings.
Phoenix
They would then be transported to Tucson, where one of the shuttle vans would take them to @placeholder.
Immigration and Customs Enforcement
@placeholder officials say politics played no role in the operation.