In what it called its largest crackdown to date on child prostitution, the FBI announced Monday that a nationwide operation over the weekend resulted in 150 arrests, with 105 children rescued. Authorities said the operation, which took investigators to race tracks and truck stops, also targeted the use of social media sites for child prostitution activity. Overall, the three-day undercover roundup Operation Cross Country took place in 76 cities and involved 230 law enforcement units, according to the FBI. “Child prostitution remains a persistent threat to children across America,” said Ron Hosko, assistant director of the FBI’s Criminal Investigative Division. “This operation serves as a reminder that these abhorrent crimes can happen anywhere and that the FBI remains committed to stopping this cycle of victimization and holding the criminals who profit from this exploitation accountable.” The ages ranged from 13 to 17 and included 28 searches with 129 seizures of cash, drugs, vehicles and firearms, he said, and those arrested face a variety of charges, including pimping.