CHUNIAN, PAKISTAN (Reuters) - Pakistani police have detained 20 suspects as they investigate the possibility of a serial killer being behind the suspected murder and sexual assault of three boys in a district which has a history of child abuse and abduction.

The body of eight-year-old Muhammad Faizan was found on an industrial estate, after he went missing on the way home from nearby shops. The remains of two more boys were found nearby.

Local media reported three other children from the area had been missing since the middle of the year and another child had disappeared late last week after the bodies were found.

“Recovering the three bodies from the same spot indicates that there might be a serial killer involved in this episode,” regional police officer Zulfiqar Hameed told Reuters.

District Police Officer Zahid Nawaz told Reuters on Monday that DNA samples of the 20 suspects held in custody had been sent for testing.

Hundreds of people demonstrated about the killings last week, blocking off streets and damaging shops.

“I nurtured my child for eight years ... I cannot bear this, I want justice,” Amtal Salam, the mother of Faizan, told Reuters on Thursday in the living room of her family home that overlooks the grave of her young son.

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Chunian, where the bodies were found, is located in Kasur, a district just south of the city of Lahore, that has been hit by waves of sexual assault and violence against children, which many locals say has continued due to a culture of impunity and lack of action in finding perpetrators.

Videos of hundreds of local children being sexually assaulted were found circulating in 2015, which a senior child protection official at the time called the worst child abuse incident in Pakistan’s history.

Last year, the body of a 7-year-old girl was found in a garbage dumpster, which police said was the 12th incident of a girl being abducted, raped and killed in Kasur in a year, and sparked violent protests. A man was convicted of the murder and executed.

Child advocates say Pakistan has a serious problem with child abuse, with child protection watchdog Sahil reporting more than 3,800 cases of sexual abuse and violence against children cases in 2018.

“Child abuse is a huge, huge challenge, not just in Kasur, but these cases are coming in a lot and are being reported in Punjab on a daily basis,” said Sarah Ahmad, chairperson of the Child Protection and Welfare Bureau for Punjab, the province in which Kasur is located.

Locals say children are fearful of going outside.

“Announcements have been made that parents should escort their children to school,” said Shehnaz Bibi, a woman from a village near Chunian. “The children are afraid to go to the mosques; they are afraid to go to school.”

Prime Minister Imran Khan has vowed law enforcement will be held accountable and said a major overhaul of district police was under way as well as an investigation into the incident.