A French judge, a forensic expert, and Jose Miguel Etxeberria's relatives were among those present for the search today near the village of Labrit in southwest France.
A recent anonymous witness account to a journalist reportedly prompted the search.
Spain's National Court reopened the case of Etxeberria's disappearance last year at his family's request, according to Spanish media reports.
Etxeberria, who went by the alias "Naparra," was a member of Comandos Autonomos Anticapitalistas, a spinoff of Basque separatist group ETA. He is thought to have been killed by a Spanish anti-terror group.
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