Martha’s Vineyard school authorities have confirmed the exclusion of four high school students for six months over alleged drug infractions, although the exact nature of the offenses remains vague and contentious.

The four were barred from the school for the remainder of this school year and the first three months of next year, as a result of an investigation which began in early April.

According to the superintendent of schools, Dr. James H. Weiss, who this week completed a review of the cases, they involved a small amount of marijuana.

An aerial drug sweep of the Island this month by the Massachusetts State Police and federal Drug Enforcement Agency (DEA) task force found 169 illegal marijuana plants. Authorities are still investigating who planted the crops and have yet to make any arrests or issue summonses.

“There will be charges, maybe this week,” said state police Sergeant Jeff Stone, also head of the Martha’s Vineyard Drug Task Force. “But as of right now the investigation is ongoing.”

Six people — three from the same Vineyard Haven family — were arrested on felony drug charges earlier this week following one of the largest heroin busts in Island history.

Members of the Martha’s Vineyard Drug Task force executed a search warrant at the Garde home on Spring street in Vineyard Haven just after 6 p.m. Tuesday and seized nearly $70,000 in heroin, cash and other drugs. Officers arrested three members of the Garde family and three other suspects for alledgedly running a drug operation out of the home.