DENVER - Two Colorado fourth graders were busted for selling marijuana at their elementary school, prompting officials today to urge adults to keep their weed locked away from kids.

School officials said a 10-year-old fourth grade boy brought a small quantity of leafy marijuana to Monfort Elementary School in Greeley, Colorado, on Monday.

"He sold it to three other fourth graders on the school playground, which resulted in a profit to the young man of $11," John Gates, director of safety and security for the Greeley-Evans School District, told ABC News.

The next day, Gates said one of the three young buyers brought a marijuana edible to school and gave it to the boy who sold the pot on Monday. That boy took a bite, but did not suffer any ill effects, Gates said.

Both boys apparently got the weed from relatives, according to Gates.

"Both of these kids took the marijuana without the consent of their grandparents," said Gates.

Gates said the four students involved will be suspended for a "significant" number of days, but declined to say exactly how long the punishment would be. Initially police were called, but officials have determined the incident will not he handled as a criminal matter, he said.

"We hope to send a good message here without ruining anybody's lives. The message we really want to get out here to the adults is, 'for crying out loud, secure it,'" Gates said.

Adults 21 and older have been able to buy recreational marijuana legally in Colorado since Jan. 1.

In a letter sent home to parents, Monfort Elementary School Principal Jennifer Sheldon said no student was injured.

"We know that many adults have greater access to marijuana since the change in the drug's legal status in Colorado," Sheldon wrote. "We urge all parents, grandparents and anyone who cares for children to treat marijuana as you would prescription drugs, alcohol or even firearms. This drug is potentially lethal to children, and should always be kept under lock and key, away from young people."

The side effects of edible marijuana - which can be far more potent than smoking a joint - have been raising new concerns after two recent deaths in Colorado. In one, a 19-year old college student died when he jumped off a hotel balcony after eating a marijuana-laced cookie. In the second, Richard Kirk, 47, was charged with shooting and killing his wife while she called 9-1-1, telling police her husband had consumed pot-infused candy.

Colorado's legislature is currently considering new safety regulations for marijuana edibles, including bills requiring stronger warning labels and lowering the amount of THC permitted in food.

The Associated Press contributed to this report