DETROIT – Glitz and glamour stole the spotlight at the North American International Auto Show in downtown Detroit, but something sinister was going on under the hood.

A police investigation revealed a human trafficking operation during one of Detroit's most popular events.

Now that the auto show is over and the undercover operation is complete, the FBI is sharing exactly what happened in Detroit and its suburbs. In some cases, it even involved children.

The operation was kept quiet as 12-15 police agencies worked together during the auto show last month to catch human traffickers and save lives. During the auto show, agents said, there's typically a 150 percent jump in the number of people offering sex.

At the time of year when the world descends on Detroit, auto show insiders, reporters and prospective customers bring a huge mix of a crowd that can be tempting to some people.

"When you're drawing in a large number of people, and more specifically, male clientele, they're traveling away from their families," Michael Glennon, supervisory special agent for the FBI, said. "They tend to flock to situations such as that."

Glennon said those situations include hiring women for sex, but it isn't always prostitution. Many of the women trafficked during the auto show are young girls and minors.

"There's typically 200-250 advertisements per day," Glennon said.

Glennon is part of the Violent Crimes Against Children task force and coordinator of the human trafficking division.

"The network is becoming more and more complex," Glennon said.

He said the pimps and human traffickers work together, warning each other online and on social media when the FBI is getting close.

"The weather reports are police activity," Glennon said. "So if there are thunderstorms in Canton or it's cloudy with a chance of rain in Romulus, they are illustrating that there is police presence or anticipated police presence. (It's) a way of warning everybody."

Glennon said the offenders know the tags of police cars and have pictures of FBI vehicles. He said they'll often post that information online.

Undercover agents made arrests at cheap motels and fancy hotels during the auto show.

"Be it from Southfield to Warren to Sterling Heights or down to Romulus," Glennon said.

The three-day undercover operation was a success.

"(We) identified four to five pimps or exploiters and made 22 arrests during the period," Glennon said. "We identified approximately 14-15 potential adult victims of human trafficking. We were able to recover two children involved in sex trafficking."

Glennon said the children recovered were 15 and 16 years old and had been brought from another city into the area.

When the children and the women were rescued from the situation, experts went in to help them get their lives back together so they wouldn't be victimized again.

Agents will be back to work at next year's auto show, as at well as many other upcoming undercover operations. The message they want to get out is, "You need to stop exploiting our kids."

"We are dedicated to eradicating human trafficking in our area," Glennon said.

The National Center for Missing and Exploited Children estimates that about 10 percent of people involved in the sex trade industry are under the age of 18.