Officers responded to the area on Friday night after receiving reports of people using an axe and spray paint to damage the cross, according to a statement from the Riverside Police Department. Police say callers described the three to four suspects as "Native American males in their 20s."
The cross was spray painted with several messages, including "native land" and "serra was a pedophile murderer," a reference to the cross' namesake, Saint Junipero Serra.
Other statues and tributes to Serra, an 18th Century Franciscan priest responsible for founding nine of the 21 Catholic missions in California, have been targeted.
Earlier this month, activists toppled a statue of Serra from its perch on Olvera Street in downtown Los Angeles.
The suspects in the Riverside incident fled down the opposite side of the mountain and were possibly seen leaving in a light colored sedan, police said.
Anyone with information regarding the vandalism or those responsible are asked to contact detectives at (951) 353-7100.