Police say they are investigating a report that a northern California high school student mixed her cremated grandfather’s ashes into homemade cookies and shared them with several classmates.

The Davis police lieutenant Paul Doroshov on Wednesday said two students baked the cookies and shared them with at least nine classmates at their public charter high school near Sacramento on 4 October.

Doroshov said the Da Vinci Charter Academy students’ motive was unknown but they were unlikely to be charged with a crime, even if one can be found that would apply to the incident. He said police would let the school handle the matter.

The principal, Tyler Millsap, told parents in a letter that the students were remorseful and that “this is now a personal family matter”.