The attempted theft of the UNESCO World Heritage-listed artwork was discovered over the weekend after visitors to the Los Escolares Cave noticed the damage to the anthropomorphic painting of a swallow.
According to 'The Local', the painting showed evidence of someone having tried to chip away at the image with a pick, and fine dust and rock fragments were spotted on the floor.
Mayor Juan Caminero of the Santa Elena in Spain's southern Jaen province said the painting was now "irreparable" and condemned the act of vandalism as "heartless", Spanish daily La Vanguardia reported.