Six young men's ancient remains were discovered face-down, with their hands bound, and covered in stones in a cave on the Spanish island of Gran Canaria. The bones have baffled archaeologists for years, and they are desperate to solve the mystery.

Evidence from the Caleta de Arriba site suggests that a terrible death occurred there centuries ago, maybe before the Spanish conquest of the archipelago off the coast of northwest Africa in the 15th century.

They are not buried strictly speaking... Veronica Alberto, who is in charge of the excavation, described this technique as a funerary one that "denotes very strong symbolic violence."

She told Reuters that the bodies had been thrown stones after being forcibly placed on the uneven area. On some of them, the limbs were bound or strapped.

"It might be an indigenous burial, but given the characteristics of the archaeological site, we need to broaden our thinking and take into account the possibility that they could be from other post-conquest eras, such as the 16th, 17th, or 18th centuries," Alberto continued.

Without artefacts, researchers are waiting for radiocarbon dating studies on the bones to assist them determine the time period.

The fact that they only discovered men led the archaeologists, who operate on the incline using safety ropes, to conclude that it was not a typical burial site. All six of the individuals had powerful arms, which indicated that they engaged in similar physical activity.