Colombian authorities are exhuming dozens of graves to determine whether the dead were civilians who security forces falsely claimed were guerrillas.

Authorities say soldiers killed thousands of civilians between 1998 and 2014 under pressure from their commanders and then claimed the victims were members of the FARC guerrilla group. They planted weapons on their victims and dressed them in fighters’ uniforms in a scandal Colombians have dubbed Falsos Positivos, or “False Positives.”

The pace of killing increased from 2005 to 2009 under President Álvaro Uribe, who led an offensive against the Revolutionary Armed Forces of Colombia, or FARC. The country’s Special Peace Tribunal, created under the 2016 peace accords that ended Colombia’s 50-year conflict, announced Saturday it had begun the exhumation of more than 50 bodies, the largest such operation to date.

The work began last week at the Catholic Cemetery of Las Mercedes in Dabeiba, a town in the northwestern department of Antioquia, the tribunal said in a statement. It came after the panel heard “a series of voluntary testimonies,” including one from a former soldier who said he knew of false positives in the town.

The soldier, who was in custody, accompanied authorities to the cemetery, located on a small mountain shrouded in fog, a human rights activist who was at the scene told The Washington Post. He spoke for an hour about his role in covering up civilian deaths.

Activist Adriana Arboleda, who represents victims through the local Legal Freedom Corporation, called the exhumation “an important step.”

“The tribunal is proving that it’s bringing to light cases that had been and would have remained unpunished,” she said. “It offers hope that the country will be able to know the truth and recover bodies. Things that victims’ families have long yearned for.”

The tribunal said the first seven bodies of the more than 50 victims believed to be buried in the cemetery had been recovered. Most victims were between 15 and 56 years old, the panel said; some were disabled.

Colombia’s main cities have been beset in recent weeks by mass demonstrations against the government of President Iván Duque — in part, protesters say, because he has failed to fully implement the peace accords signed by his predecessor, Juan Manuel Santos. Duque is a member of Uribe’s Democratic Center Party.

Dozens of demobilized FARC members, including some who participated in the peace negotiations, have retaken arms and returned to the jungle to resume the fight. More than 700 activists, indigenous leaders and demobilized FARC guerrillas have been killed since 2016.

Guillermo Botero, Duque’s defense minister, resigned in November after evidence emerged that children had died in operations against dissident FARC groups. The New York Times reported in May that military commanders had ordered troops to kill more criminals and militants, suggesting they would accept more collateral damage.

The exhumations had been long awaited by victims of the armed conflict as a next step beyond taking testimony.

Dozens of soldiers have appeared before the tribunal since 2016 to be judged under transitional justice, which offers them reduced punishment if they collaborate. Investigations into false positives started last year.

“We have talked to more than one hundred military men,” Alejandro Ramelli, a tribunal magistrate, told the national newspaper El Espectador. “They have revealed to us dozens of incidents, but we now have to confirm that what they are saying is true.”

The testimony of more than 160 soldiers has helped authorities identify some 400 victims to date, the tribunal said Saturday. The panel said last year that 1,944 troops, involved in more than 2,500 false positive cases, were willing to cooperate with the investigations.

The attorney general’s office has reported more than 2,200 victims since 1998. Activists say the number is closer to 5,000.

Authorities entered the Dabeiba cemetery accompanied by soldiers who had been ordered to prove their testimonies, Colombian media reported.

Ramelli told El Espectador that the bodies would be identified and more witnesses would be interviewed.

The 2016 peace accords have polarized Colombia, and the tribunal has been at the center of the controversy. Critics say the perpetrators of war crimes are likely to get less punishment than they deserve. Others say the offers of leniency to those who cooperate are bringing to light crimes that would otherwise be forgotten.

“The exhumations show that crime perpetrators are trusting the special tribunals,” said Kenneth Burbano, director of the Constitutional Observatory of the Free University of Colombia and a former auxiliary tribunal magistrate. “In the middle of protests, it’s a clear signal that the government has to understand: All it has to do is back the search for truth.”