(CNN) Rumors had swirled around Andreas V. for years; locals whispered about his behavior with children, to whom he offered pony rides and quad bike tours.

But few had any idea of what police now say was taking place inside his cluttered camper van in the heart of the Luegde Forest in central Germany.

Police in nearby Lippe say they believe Andreas V. abused dozens of children over decades, even using his six-year-old foster daughter as "bait" to lure in his young victims. In December, German police arrested Andreas V—German privacy law does not allow police to give the full names of suspects—and he remains in police custody, while the list of his alleged victims continues to grow.

His lawyer declined to comment on the allegations.

The story of Michaela

One alleged victim, who we'll identify only as "Michaela" to protect her and her family's privacy, said she first met Andreas V. 30 years ago when he was 16 and she was 9.

"My father had a camper with my grandparents at the camping site, adjacent to Andreas' family van. We were there a lot. It was a real camping community. Like a big family," she told CNN in a phone interview.

"My father allowed him to stay at our house and, for some reason, Andreas always slept in my room. That's when he touched me for the first time."

She says she was 11 when the abuse began.

"I told my father: 'I don't want Andreas to sleep with me because he touches me.' But my dad said: 'No, that's not true. He would not do that.' He just ignored me," she told CNN, her voice breaking. "And if you are not believed as a child, you give up hope at that age of 16 or 17. So, I kept silent for all those years. I did not tell anyone."

Michaela says her father has since been questioned by the police. Prosecutors have confirmed that the father of one victim had been questioned, but would not confirm if it was Michaela's father. CNN's attempts to contact him have not been successful.

German police believe Andreas V. went on to become the ringleader of a pedophile gang that used his family's camper van as its base of operations for decades, abusing dozens of children and recording their crimes for profit on the dark web.

Authorities say they collected ten computers, nine mobile phones, more than 40 hard drives and more than 400 additional data carriers as evidence from Andreas V and two other men.

The case has scandalized the nation, especially after police recently admitted that some of the data confiscated as evidence has been "lost" while in police hands.

Germans are left wondering how both law enforcement and social services failed to stop the abuse, despite numerous red flags.

Hiding in plain sight

In November of last year, police received a report that Andreas V. had sexually abused a six-year old child who had gone to his home for a play-date with his foster-daughter; he was arrested several weeks later.

When investigators broke the lock on the camper van where he lived, they found a jumble of furniture and clothing, along with 15 terabytes of data stashed in various hiding places, including a USB stick embedded in the joint of a chair, police said in a press statement following the arrest.

Two other men, a 48-year old and a 33-year old, were arrested on suspicion of exchanging child pornography with Andreas V.

"The investigations so far give reason to fear that the perpetrators have committed more than 1,000 acts of abuse, going back to the year 2008," police said in an initial statement.

"In addition to investigating allegations of serious sexual abuse, more lines of investigation have emerged including child pornography, extending to the internet. Furthermore, the offices responsible for child care in the district of Lippe are being investigated for possible criminal acts," said the statement.

But that was only the beginning.

More cases come to light

Parents had tried to raise the alarm about Andreas V. before.

In 2016, a local father, Jens Ruzsitska, said he had seen Andreas V. groping children at a birthday party. Ruzsitska punched him and accused him of "feeling up" the children before storming out.

Police confirmed to CNN that Ruzsitska filed a police report of the incident at the time but say no further action was taken.

Asked why no action was taken back then, the local prosecutor told CNN: "All evidence is being pursed and taken seriously."

Despite this allegation against him, Andreas V. was granted permission to become the guardian of a six-year-old foster daughter that same year.

The local Youth Welfare Office has now launched an investigation into how Andreas V. was allowed to become a foster parent.

When contacted by CNN, the Youth Welfare Office confirmed Andreas V. had been reported twice in 2016 for "possible child endangerment," even as Andreas V was regularly being assessed by youth welfare officers. In October of that year, however, the youth welfare office found no evidence of child endangerment and granted him guardianship of the foster child.

However, District Administrator Tjark Bartels, who has responsibility for overseeing the Youth Welfare Office, told CNN there is now evidence that Andreas V.'s application to become a foster parent had been manipulated and "beautified."

"An employee has admitted that he subsequently manipulated the files of the Youth Welfare Office, adding a note to complete the file," Bartels said in a statement sent to CNN. Bartels would not clarify how the file had been manipulated, citing the ongoing investigation.

The employee has been suspended and is currently under investigation by the state prosecutor to find out what links, if any, he has to Andreas V.

Police now believe that Andreas V. not only abused the foster child he was supposed to look after, but that he also used her to lure other child victims.

According to investigators, there are at least 40 victims, aged four to 13 at the time of the abuse, including his foster daughter. Police have warned that the number of victims will likely rise as they continue to sift through his cache of recordings.

"This foster child was used as bait, to lure and attract other children," said Roman von Alvenleben, a lawyer who represents the family of one 10-year old girl allegedly abused by Andreas V. "They got to know each other at birthday parties and play dates. That's what my client's mother did. She was not aware of what was really going on."

Police lose evidence

As if failing to act on reports of child abuse wasn't bad enough, now police have admitted that evidence -- at least 155 CDs and DVDs confiscated from Andreas V.'s home -- has been lost while in police custody. The material was kept in an aluminum suitcase and a black folder that was supposed to have been sealed as evidence. It was reported as missing weeks later.

The state prosecutor launched an investigation which he said "assumes the evidence cannot be found due to careless handling and that it was not stolen, although, such a possibility cannot be excluded."

In a statement to the press, Lippe Police Chief Axel Lehman said the lost data amounted to only a small fraction of the evidence against Andreas V. and would not affect the prosecution case.

Still, he admitted, "These are blatant mistakes that have been made by police in Lippe. This stuns me and clearly it should not have happened. I express my apologies to all those who were affected."

Parents lose trust in police

For Michaela, the lost evidence is only the latest breach of trust by police.

"I have had enough about the lies. The police. The youth welfare office. The evidence that suddenly goes missing." She told CNN. "So many children suffered sexual abuse here -- children who are now psychologically scarred, for the rest of their lives. I know because that's what happened to me. That's why I'm speaking up now."

Her own painful experience seems to be part of a traumatic pattern that has unwittingly been repeated in her own family.

A photo of Michaela as an adult.

Last summer, she allowed her 16-year-old daughter to spend the weekend with other teenagers at the Luegde campsite, the community's main summer retreat, on the condition that she stay well away from Andreas V.'s camper van.

Weeks later, her daughter broke down in tears and told her she had blacked out after drinking alcohol and woke up to find an adult man on top of her while another man watched.

Michaela says she immediately filed a police report and informed the Youth Welfare office but the case was dismissed for lack of evidence. In a letter seen by CNN, the local prosecutor informed Michaela and her daughter last year that "there is no evidence of rape by the accused," adding that there was no evidence the teenager had either verbally or physically resisted the alleged assault.

"But does a girl fight back when she's incapacitated?" asked Michaela. "When there are two men in the room? How is she supposed to fight back?"

It was only after Andreas V.'s arrest weeks later that Michaela discovered that the two men her daughter had identified had also been arrested and linked to Andreas V.'s alleged pedophile network.

Police have now reopened the case, but it has only fueled her anger and distrust of the police.

"We don't know if the evidence police have -- or whatever they lost -- contains any pictures of my daughter," Michaela told CNN. "Or even myself. It is a nerve-wracking situation. It could well be that they discovered evidence from all those years ago."

Abuse on the dark web

Police are now investigating whether Andreas V. operated a business recording the abuse and selling videos of it on the dark web.

German prosecutors have just concluded the trial of several administrators of Elysium, one of the largest chat forums in the world for child abuse and pornography. Based in Germany, the site had racked up more than 110,000 users before it was shut down in 2017. Four men were convicted on various charges of child pornography and operating an illegal site, with each sentenced approximately to 10 years in prison.

For families of the Luegde victims, there are too many troubling questions that have not yet been answered, including whether their abuse was recorded on the videos and photographs now held by police.

"Why are CDs disappearing? Who was on those CDs? Is someone being protected? We have to ask these questions," said lawyer Roman von Alvensleben.

"Fifteen terabytes of data were found, reportedly videos were sent out and possibly a business was operated. It must become clear who had access to that data and who else was involved. I suspect there are still many other connections," von Alvensleben added.

A trial date for Andreas V. has not yet been set; the investigation continues to expand as new victims come forward, and investigators have warned that the number of victims is likely to rise.