US LAW enforcement has redoubled efforts to fight what they worry could be one of the biggest menaces at next month's Super Bowl: sex trafficking.

Hundreds of thousands of visitors are expected to descend on New Jersey for the February 2 football game. Many believe the state's sprawling highway system, proximity to New York City and diverse population make it an attractive base of operations for traffickers.

"New Jersey has a huge trafficking problem,'' said US Republican Chris Smith, who is co-chairman of the House anti-human trafficking caucus. "One Super Bowl after another after another has shown itself to be one of the largest events in the world where the cruelty of human trafficking goes on for several weeks.''

Law enforcement in New Jersey has worked for years to battle forced prostitution. The state strengthened its human trafficking law in early 2013, but it hit a roadblock in August when a federal judge ruled that a portion of the law that pertains to commercial sex ads posted online may conflict with federal legislation. The state is appealing.

There are scant statistics and much debate over how much sex trafficking increases during a Super Bowl or other large sporting event, but it's been enough of a concern to prompt New Jersey and previous Super Bowl host cities to pay attention to it.

Danielle Douglas, a speaker and advocate who identifies herself as a sex-trafficking survivor, said any major sporting event attracts sex traffickers looking to make money.

"The Super Bowl is a huge, huge arena for sex trafficking,'' Douglas said. Some visitors "are coming to the Super Bowl not even to watch football - they are coming to the Super Bowl to have sex with women, and/or men or children.''

Soon after the announcement that the 2014 Super Bowl would be held at MetLife Stadium, New Jersey officials set up training for legions of law enforcement personnel, hospitality workers, high school students, airport employees and others on identifying the signs of sex trafficking.

Local houses of worship are handing out fliers notifying congregants of warning signs, and truckers are being trained to look for people - mostly women but also men - who may be held against their will.

Sex trafficking, to be prosecuted as such, must involve - unlike prostitution - not only a buyer and seller of sex but also a pimp or trafficker controlling the transaction, according to the New Jersey attorney general's office.

Officials are also warning the public to watch for people who are forced into labour and individual pimps exerting control over young women and men who are oftentimes underage.

"We've enlisted, basically, every service provider that people coming to the Super Bowl are going to run into,'' Acting Attorney General John J. Hoffman said. "There are a lot of eyes that are going to be on their activities and going to be on spotting potential victims of this crime.''

The Super Bowl task force convened by Mr Hoffman's office is composed of state, local and federal law enforcement officers, community groups, social workers and others. Bergen County Prosecutor John Molinelli said ads are starting to pop up on Internet sites and law enforcement officials are gleaning information from them.

"When you're about ready to have 400,000 men come to this area of the country,'' Mr Molinelli said, "you're invariably going to have more people try to take advantage of that by providing prostitutes and prostitution.''

Officials in Texas, Louisiana and Indiana strengthened efforts to combat sex trafficking ahead of previous Super Bowls. In Arizona, which will host the 2015 Super Bowl, US Senator John McCain's wife, Cindy, has been speaking out, calling the Super Bowl the "largest human-trafficking venue on the planet.''

It is difficult to ascertain the exact number of trafficking cases in a given year or place because so much of it goes unreported. In 2012, the Polaris Project, a nonprofit that works to combat human trafficking, received 20,652 calls reporting trafficking to its hotline, 330 of which were from New Jersey, CEO Bradley Myles said.

"The overall size of the phenomenon in the United States is much more significant than statistics show,'' Mr Myles said.

Polaris plans to add additional staffers to the hotline in February, but the organization has seen only a modest uptick in calls during previous Super Bowls, Mr Myles said.

In December, Kathleen Friess led a two-hour presentation in Hamilton Township for hotel and nightclub employees and tried to dispel notions of what human trafficking looks like. Often, Ms Friess said, it's a local woman forced into sex work by a man she initially thought had romantic intentions. Other times, it's a woman from another country whose family is threatened.

Ms Friess told the employees to look for women who may not be in control, who look frightened and may exhibit signs of physical abuse. Victims are often runaways, the impoverished, abuse victims or those living in the country illegally, she said.

"You guys are at that front line, seeing them coming and going,'' Ms Friess said. "You're in a position to prevent human trafficking.''

Ronald Moore, the security manager at the Grand Summit Hotel in Summit, said he plans to replicate the presentation for his staff. A former police officer, Mr Moore said the hotel has been preparing for the possibility of crime during Super Bowl week.

"You're going to have the potential for everything from stolen goods to assault to check fraud. Everything you can imagine is going to be happening,'' he said. "You have to be aware.''

Jane Wells, a filmmaker who recently released Tricked, a documentary about human trafficking, said she wants law enforcement to focus on the crime all the time, not just around sporting events.

"This is a 365-day-a-year problem,'' Wells said.

Originally published as 'Many going to Super Bowl for child sex'