PITTSBURG — Seven fifth-graders at Stoneman Elementary School were suspended after sharing nibbles of a sugary treat made of Fruity Pebbles cereal that contained marijuana, school district Superintendent Barbara Wilson said.

The fifth-grader who brought the treat to school Monday got it from her adult sister, police Lt. Brian Addington said. The older sister told police she received it from a medical marijuana dispensary. The fifth-grader was aware the treat contained marijuana, he said.

Police are investigating whether the older sister had a legitimate card to obtain the marijuana. No arrests have been made. The treat accidentally fell out of her purse, Addington said.

The school children who tried the treat had "minute amounts, basically pieces of the pebbles," Addington said. A sample of the treat was obtained by police and confirmed to contain THC, the primary intoxicant in marijuana, by the county's crime lab, he said.

A couple of children who witnessed the incident alerted school staff, who contacted police and paramedics, Wilson said.

The child who brought the treat to school was suspended indefinitely while police complete their investigation, Wilson said.

The others were suspended for a day for not alerting school staff about the situation.

Paramedics checked the vital signs of students who had sampled the treats and the results were within normal limits, Wilson said. The children were released to their

Stoneman Principal Donna Marshall sent out a letter reminding parents to teach their children to notify adults when they hear of something dangerous.

The incident also shows that adults should be careful with dangerous substances when around children, Addington said.

Contact Paul Burgarino at 925-779-7164.