South Korea's top public prosecutor on Tuesday apologized over what he described as a botched investigation into the enslavement and mistreatment of thousands of people at a vagrants' facility in the 1970s and 1980s nearly three decades after its owner was acquitted of serious charges.

The remarks by Prosecutor General Moon Moo-il were the government's first formal expression of remorse over one of worst human rights atrocities in modern South Korea. They add pressure for parliament to pass legislation to start a deeper inquiry into what happened at the now-closed Brothers Home, whose owner was exonerated from serious charges amid an obvious cover-up orchestrated at the highest levels of government.

"The past government created a (government) directive that had no base in laws and used state power to detain citizens at the Brothers Home confinement facility with the disguised purpose of protecting them; more than that (inmates) were subjected to forced labor, while experiencing brutal violence and other harsh violations of their human rights," Moon said, stopping several times during his statement while appearing to hold back tears.

"I accept with a heavy heart the results of our committee (on past cases) that the prosecution then caved into pressure from above and closed its investigation prematurely. Even on the charges that were included in the indictment, the defendants weren't properly punished during the trials. This was a process that cannot be described as democracy."

Moon delivered his apology in a meeting with about a dozen former inmates, most of whom who were children when they were snatched off the street by police and city officials and locked up at Brothers Home. They spoke of their experiences at the facility, including slave labor and near-daily assaults, how their sudden disappearance ruined their families, and how they have struggled with their lives since.

"I have no friends because I couldn't go to school," said Park Sun-yi, who spent more than five years at Brothers Home after being snatched by police at the age of 9. "We have no families to go to at Chuseok," she said, referring to the Korean Thanksgiving.

No one has been held accountable for hundreds of deaths, rapes and beatings at Brothers Home that were documented by an Associated Press report in 2016. The AP report was based on hundreds of exclusive documents and dozens of interviews with officials and former detainees, which showed that the abuse at Brothers was much more vicious and widespread than previously known.

Military dictators in the 1960s to 1980s ordered roundups to beautify the streets, sending thousands of homeless and disabled people and children to facilities where they were detained and forced to work. The drive intensified as South Korea began preparing to bid for and host the 1988 Summer Olympics. Brothers Home, a mountainside compound in the southern city of Busan, was the largest of these facilities and had around 4,000 inmates when its horrors were exposed in early 1987.

Kim Yong Won, the former prosecutor who exposed Brothers, told AP that high-ranking officials blocked his investigation under direction from the office of military strongman Chun Doo-hwan who feared of an embarrassing international incident on the eve of the Olympics.

Death tallies compiled by the facility claimed 513 people died between 1975 and 1986, but the real toll was almost certainly higher. Kim's investigation records include transcripts of interviews of multiple inmates who said officials refused to send people to hospitals until they were nearly dead for fear of escape.

Kim, now a lawyer, wasn't able to indict Brothers Home owner Park In-keun or anyone else for widespread abuses at the facility and was left to pursue much narrower charges linked to embezzlement and construction law violations and confinement at the construction site where inmates worked.

Former Brothers Home inmates have received no compensation. They have been calling for a new investigation to establish the government's responsibility more clearly and create a base for compensation.

Seoul's previous conservative government had refused to revisit the case, saying that the evidence was too old and expressing concerns over financial burdens. But the prosecution has recently been reviewing its handling of Brothers Home and other past cases suspected of human rights violations or abuse of investigation power as it faces greater pressure for reform under liberal President Moon Jae-in.

Moon Moo-il, the top prosecutor, last week asked the Supreme Court to re-examine the trial of the late Brothers Home owner. Park In-keun, who died in 2016, had been acquitted in 1989 of charges linked to illegal confinement of inmates but served a short prison stint for embezzlement and other relatively minor charges.

The court then ruled that Park was abiding by a 1975 government directive that instructed police and local officials to round up vagrants.

The Supreme Court has not decided whether to reopen the case. Moon's request for an "exceptional appeal" allows the court to correct grave mistakes in interpretation of law though it cannot impose new punishment on the defendant. If the court accepts the case, a finding that the government failed to protect the constitutional rights of the former inmates could boost their push for compensation.