The FBI arrested 281 pimps and rescued 168 children during a nationwide crackdown on child sex trafficking.

The annual crackdown targeted 106 cities across the United States and overall, the federal agency has rescued almost 3,600 children through eight total operations that are part of "Operation Cross Country," CBS News reports.

"These are not faraway kids in faraway lands," FBI Director James Comey said. "These are America's children." The director added, "There is no more meaningful work that the FBI participates in than rescuing children."

According to NBC News, many of the children were never even reported missing, while some went missing while in the child-welfare system.

"Many of these children have been abandoned, often abused and neglected," John Ryan, of the National Center for Missing and Exploited Children, said. "Many of these traumatized children run away because they believe it's the best option for them."

Along with the children rescued, Operation Cross Country has seized assets worth more than $3 million and have made 1,450 convictions.

Still, Comey noted that he is worried about how common it is becoming for the Internet to be used for child sex trafficking.