BOULDER CITY, Nev. -- An exclusive FOX5 investigation uncovers new questions about a Boulder City teacher accused of sexual assault.

Were there warning signs that were overlooked that several students were possibly being abused?

Charles "Rick" Rogers was arrested on charges of child pornography and assault after an anonymous tip. But did officials know something was up long before then?

A source close to the investigation told FOX5 before the case exploded that parents had come forward about their concerns with Rogers, and the teacher's behavior may have been checked out before.

The Clark County School District looked into the claims, but parents said nothing was done about it, according to the source.

District officials said they could not talk about Rogers’ personal file but said they take every allegation seriously. But they said if there is no concrete evidence to go on, their hands are tied.

"Predators are going to put themselves in positions of trust and authority, where they can gain access to children. They gravitate to those jobs," said child advocate Terri Millers.

Millers said that's because of loopholes in the law. For example, she said districts in Nevada usually do one full background check when hiring, but the employee is seldom checked again. That person could even have a complaint filed against him or her with police, and the district may never know about it.

One high school softball coach in Boulder City said he would like to see more background checks, even though he said the first check is tough.

"Just to get a coaching background check it took a lot of work -- from the fingerprinting to references you have to have, the police background check. They go pretty thorough," said softball coach John Yesh.

But if a teacher has worked in another state, a muddied past may not follow that teacher to a new job in Nevada because of blurred rules and loopholes.

Millers said parents should trust their instincts.

"When a kid is not feeling safe, and you have a gut feeling something is going on, that's when you start watching and documenting," Millers said.

The source said about six possible victims are being interviewed this week.

Rogers will be in court on Tuesday.

Police said they are still trying to identify victims found in photographs and videos.

To contact Boulder City investigators, go to fox5vegas.com.