The investigation into whether the man violated historical heritage laws started in May after officials discovered photos online, CNN reported.
The rock illustrations, protected by a heritage register, date back centuries, with some estimated to be over 6,000 years old, according to The Daily Beast.
According to the Guardia Civil, spilled water on the limestone walls can cause “irreparable damage” as salts dissolve and rise to the surface, forming a crust when the liquid evaporates.
