Four adults have been arrested after a school principal found 70 grams of crack cocaine on a seven-year-old, police say.

The boy's parents and two uncles were arrested Monday after he brought the drugs to Trenton's Parker Elementary School.

Police say they responded to the school after the boy's 10-year-old sister saw the drugs and reported the incident to the principal's office. Police say she was afraid her brother would get in trouble.

Police say The Division of Youth and Family Services has taken custody of the siblings.

The identities of those arrested, who are between the ages of 19 and 27, have not been released. They've been charged with endangering the welfare of a child and drug offenses.

Police say the investigation is ongoing.