Vienna, Austria ? Trafficking people for forced labor and sexual slavery has become the world’s No. 2 most lucrative crime, and terrorists are using shadowy underground networks to move around, a senior U.S. counter-trafficking official warned Tuesday.

Human trafficking, particularly the smuggling and enslavement of young women for prostitution, is tied with weapons smuggling as the second-largest illegal moneymaking activity, said T. March Bell, the Justice Department’s senior special counsel for trafficking issues and civil rights.

Only the narcotics trade reaps more profits for organized crime, but traffickers are earning billions of dollars exploiting tens of millions of victims each year, Bell said, calling it “the No. 1 human rights issue today.”

The profits are huge, he told reporters, citing the example of a brothel owner in Southeast Asia who typically might pay $8,000 for a young woman. “We think that owner can make a $200,000 profit on that $8,000 investment,” Bell said.

Terrorists also are taking advantage of sophisticated smuggling operations to obtain counterfeit passports and transit to Western countries to plot or carry out attacks, he said.

Although the traffickers are dealing mainly with young women peddled to brothels, or men, women and children sold into virtual slavery on farms and in factories, “they’re moving any kind of people for a price,” Bell said. He declined to elaborate, citing classified intelligence.

Despite the massive scale of the crime, law enforcement agencies are having a difficult time bringing perpetrators to justice, in part because of corruption within their own ranks.

In the former Yugoslavia, there have been numerous cases of corrupt police officers engaged directly in the sex trade or willing to alert a bordello operator to an impending police raid in exchange for a bribe.

Police officers in many poor, developing countries where trafficking is widespread tend to be poorly paid, making them particularly susceptible to bribes, Bell said. In Cambodia, the average officer earns just $35 a month, he said.

Law enforcement is trying to counter that by improving the training of police officers, ensuring they are paid professional salaries, and making anti-trafficking units the envy of police forces by equipping them with the latest technology and holding them to higher standards, Bell said.

While the most effective weapon against traffickers is “street-level law enforcement,” police agencies increasingly are turning to undercover operations in an effort to infiltrate clandestine rings, often using officers who pose as brothel customers or as middlemen looking to hire cheap laborers, he said.

In the United States and many European countries, ex-victims are getting increased protections and refugee status in the hopes of persuading them to testify against their former captors, Bell said.

A key challenge is winning the trust of former victims who all too often are “frightened, scared, intimidated and coerced” by traffickers who confiscate their identity papers, skim their earnings and threaten them or their families with violence, he said.

“Unless a victim feels safe, they’re not going to provide much information to prosecute the perpetrators,” he said.