And that's the way the cookie crumbles.

Some students at a California high school may be swearing off cookies forever, after a classmate allegedly baked her grandfather's ashes into a batch of the sweet treats and offered it to them, reported the Tribune News Service on Tuesday (Oct 16).

A female student at Da Vinci Charter Academy, a public charter high school, took the baked goods to school on Oct 4 and gave them to at least nine other students, said Lieutenant Paul Doroshov from the Davis Police Department.

"Some students knew (about the extra ingredient) beforehand and still consumed the cookies," he said.

When asked about whether the allegation seemed credible, Lt Doroshov gave a long sigh and said: "Yeah."

He added that two female students took the cookies to school, according to a school resource officer. Lt Doroshov also said that the relationship between the two girls is unclear, but they are not siblings and the dead man was the grandfather of only one of them.

A student at the school, Andy Knox, told California television station KCRA-TV that he was offered a cookie when entering a class.

He assumed it was marijuana when told about a "special ingredient", but later realised what it really was.

"I didn't believe her until she pulled out the urn," said Andy.

"If you ever ate sand as a kid, you know, you can kind of feel it crunching in between your teeth. So, there was a little tiny bit of that," he said, adding that the cookie did not taste unusual though it did contain "tiny grey flecks".

Lt Doroshov said that the police are investigating and have been trying to see which penal code applies to baking human remains into food.

He added that officers considered a California penal code section regarding the disposal of human remains in an improper manner, but also said that public nuisance charges may be more appropriate.

The authorities are working with the school to determine how best to proceed, said Lt Doroshov.

Da Vinci Charter Academy principal Tyler Millsap said in a letter to parents that "this issue going on right now has been particularly challenging and our staff has responded appropriately and in the most respectful and dignified way possible for all the students and families involved".

Mr Millsap said he regretted that the story "has been taken up by the media" and said that there is no health risk to any students.

"I can say that those who were involved are remorseful and this is now a personal family matter and we want to respect the privacy of the families involved."