An Air Force Academy official says about 30 cadets are suspected of using banned substances, which is double the number of cadets the school said it was investigating in January.
Academy spokesman Lt. Col. John Bryan says the inquiry involves substances other than alcohol, tobacco or drugs prescribed to cadets. He says the review could wrap up in a few months.
Some of the cadets under investigation are reportedly intercollegiate athletes.
Bryan didn't know if any cases have resulted in charges or discipline yet. Other details haven't been released.
In 2011 the academy investigated suspected use of banned substances including Spice, which mimics the effects of marijuana. Twenty-one cadets resigned, five were kicked out, and one went to a court-martial. Results of the court-martial weren't immediately available Thursday evening.