LAS VEGAS (AP) — The FBI in Las Vegas is teaming with an advertising company donating billboard space to raise the profile of efforts to stop human trafficking in a state where brothels are legal in rural counties, but prostitution is illegal in cities such as Las Vegas and Reno, officials said Thursday.

"Anyone who calls this number will receive assistance," Aaron Rouse, the FBI agent in charge in Las Vegas, told reporters at an announcement timed to coincide with images appearing on 10 electronic billboards at busy crossroads and freeways around Sin City.

"This is not about law enforcement," Rouse said. "This is about saving lives."

The top Clear Channel Outdoor executive in Las Vegas, Adam Barthelmess, said the company donates outdoor advertising space in about 20 cities around the country, including Philadelphia, San Francisco, Phoenix, Houston, Des Moines, Iowa, and Albuquerque, New Mexico.

He called Las Vegas the first where billboards are being used to fight human trafficking.

Messages are being posted in English, Spanish and Chinese. Barthelmess estimated the value of the company donation over the one-year program at $2 million.

Toll-free calls will be fielded 24 hours a day in more than 200 languages by the National Human Trafficking Hotline, said Sandra Breault, FBI Las Vegas spokeswoman.

The hotline was started in December 2007 by Polaris, a nonprofit non-governmental organization that connects trafficking victims and survivors to support and services.

Rouse called electronic billboards a new tool amid other FBI efforts to identify victims and prosecute people who bring them across state lines. The agency has for more than a decade reported results under a program dubbed Operation Cross Country.

Last October, the bureau reported finding three minors and arresting 44 adult prostitutes in Nevada.

The FBI chief said officials believe about 70 percent of trafficking victims are forced into sex and about 30 percent are pressed into labor by criminals using force and coercion to prevent them from getting free.

A yearlong academic study of sex trafficking in Las Vegas released in February offered a glimpse into the shadowy world where underage girls, threatened by pimps, solicit for business in casinos, on streets and online.

Researchers from Arizona State University identified and studied 190 sex-trafficking victims in Las Vegas in 2014, with the average underage victim aged 16. The youngest was 12.

The report also pointed to difficulties prosecuting accused sex traffickers, with only about one in five of the 159 cases studied resulting in convictions.

The average trafficker was 29, and 80 percent had criminal histories. Most came from outside Nevada, and most of them were from California.

California state Attorney General Xavier Becerra in July called human trafficking one of the fastest-growing criminal enterprises worldwide. At the time, he announced filing criminal charges against three people accused of pimping teenagers, ages 15 to 17, through internet postings to customers in California, Texas and Nevada, including Las Vegas.