The skeletal remains of 14 people believed to be victims of right-wing paramilitaries have been unearthed in a mass grave in southwest Colombia, authorities said Friday.

The office of chief federal prosecutor Mario Iguaran said he visited the grave in a rural area near La Hormiga, in Putumayo province, 330 miles southwest of the capital, on Thursday.

Forensic experts suspect they could find more victims as they continue to search the area around the 5-year old grave in an investigation into a paramilitary militia known to operate in the area and accused of killing civilians.

Authorities said further analysis is required to establish the identities those found in the grave and to determine how they were killed.

In the last 18 months, as a peace process with paramilitary groups has advanced, investigators have discovered more than 400 corpses. More than a quarter of those have been found since June at 20 mass graves scattered across the country.

The United Self-defense Forces of Colombia, or AUC for its Spanish initials, has been implicated in the vast majority of those crimes.

The AUC entered a peace deal with the government in 2003, bringing a partial respite to the violence associated with Colombia's four-decade civil war. The country's homicide rate — among the world's highest — dropped sharply, as did the number of civilian massacres.

More than 30,000 right-wing fighters have demobilized as part of the peace process.