Israel Antiquities Authority (IAA) inspectors were shocked to find on Wednesday that the Ashdod-Yam Citadel, which is one of the most well-preserved historical sites in Israel, had been vandalized.
The ancient fortress, which dates back to the 8th century CE, was found with paint splattered across its walls.
IAA inspectors found containers and paint brushes upon arriving at the scene.
Photos have appeared on social networks of teenagers throwing a "color party" at the site.
IAA director Yisrael Hasson said that he "expects the teens and their parents to contact us through the IAA Facebook page within the next 48 hours so that we can show them how to clean up without causing any damage."
If not, he said, the IAA will prosecute them for vandalism under the law.