The father of a young girl said his daughter was given a bag of methamphetamine when she went trick-or-treating in the San Francisco Bay area on Halloween.

The father said that he found .1 gram of crystal meth in a small Ziploc pouch on Monday while he was sorting through the candy that his 8-year-old daughter collected near their home in Promenade.

Now, police in the East Bay town of Hercules are trying to determine whether the person intended to distribute the illegal drug to the child or if it was done by accident, NBC Bay Area reported.

The father "had been checking his child's Halloween candy after putting it away on Halloween night, and while checking it found the baggie and suspected it was illegal drugs. He wanted to report it," said Hercules Police Sgt. Ezra Tafesse.

The substance then tested positive for methamphetamine, "a small amount but enough to do damage to an 8-year-old girl had she gotten into it on her own," said detective Connie Van Putten, a spokeswoman for the Hercules Police Department.

According to Sgt. Tafesse, the amount of meth found is enough to charge the person responsible with a felony for possession of controlled substance.

Van Putten said detectives are examining the plastic bag that carried the meth for fingerprints. She also said that the case appears to be an isolated incident.

"We are leaning toward it being an accident, but we are not ruling out an intentional act," she said, reports Reuters. "Whoever it was may have intended to put it in somebody's candy but not hers."

Van Putten warned parents to check their children's Halloween candy before allowing them to eat it.

"You don't want to keep your children in bubble wrap, but you do need to be aware ... and go through children's candy to make sure none of the packaging has been tampered with, and that there's no needles, razor blades or anything foreign," she said.