UNITED NEWS INTERNATIONAL (UNI) — Indonesian custom officials have stopped an attempt to mail 24 decorated human skulls to the Netherlands.

The Associated Press reports officials on the island of Bali revealed the incident earlier this month.

The cartons containing the skulls were intercepted on two different times in Jan. 2018.

The labels on the cartons said the skulls were manufactured from synthetic materials.

However, experts at the Balinese Cultural Heritage Conservation Center found them to be human after examining them.

A customs official said the skulls were most likely from two locations: the province of Papua or Kalimantan region on the island of Borneo.

Kalimantan is home to the indigenous group, the Dayak.

The Dayak had been known as headhunters, and the group preserved the skulls of their victims.

At this time, no arrests have been made in the smuggling attempt.