Updated

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

Of 190 identified sex-trafficking victims in 2014, Arizona State University researchers found two-thirds were under 18 years old, one in five was brought to Las Vegas from somewhere else and more than half were never reported as missing.

A victim advocate in the Las Vegas Metropolitan Police Department, Elynne Greene, said many of the victims are products of the foster care system.

The study, made public this week, says that in 159 cases that Las Vegas police identified as sex trafficking, nearly three in four were never prosecuted.

That's because victims often fear their pimps and refuse to cooperate with police and prosecutors.