As investigators worked to determine the origin of human remains found inside a residential altar in Pasadena, California, the family that owns the property is claiming they were bought online.

KNBC-TV reported on Monday that the skull and bones were found on Sunday while responding to a report of a trespasser on the premises. But a man who identified himself as a family relative told the station that the homeowners put up the altar in keeping with the practice of Palo Mayombe, an offshoot of the Caribbean religion Santería, and that the bones were purchased on eBay.

The remains, which were laid out alongside several small statues, animal bones, incense and burned offerings, caught authorities' eye, at which point they were seized to determine their origin.

"The religious aspect of the case is not our focus," said Police Lt. Ed Calatayud. "It's the bones."

However, R. Andrew Chesnut, a professor of religious studies at Virginia Commonwealth University, told the station the altar bore signs of the Mexican cult "Santa Muerte," a growing cult in Mexico that he described as "a fusion of medieval Catholicism and native Mexican folk religion."

According to The New York Times, devotees of Palo Mayombe were blamed for a series of grave robberies in Venezuela in 2009. And the animal-conservation group the Animal Recovery Mission said animal sacrifices are common practice for the religion, calling it "Santería's evil twin."

Watch KNBC's report on the grisly discovery, aired Monday night, below.

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