Remains of at least 100 dismembered prisoners and visitors have been found in drain pipes at a jail in Colombia’s capital that houses drug traffickers, Marxist rebels and paramilitaries, investigators said on Wednesday.

Body parts were found at La Modelo jail in Bogota, one of the Andean nation’s biggest penitentiaries, as well as in jails in the cities of Popayan, Bucaramanga and Barranquilla, said Caterina Heyck, an investigator at the attorney general’s office.

“The number of victims is unknown, but we know it’s over 100 and could be considerably higher,” she told reporters in Bogota. “Remains of prisoners, visitors and others were thrown in the drainage system.”

Colombian jails are among the most overcrowded and violent in Latin America and accommodate leftist guerrillas alongside their right-wing paramilitary enemies.