AVIANO AIR BASE, Italy — Two more airmen have been court-martialed in the biggest drug case in base history.

Senior Airman Justin Marshbank, assigned to the 603rd Air Control Squadron, was found guilty on cocaine charges in a general court-martial Monday. He’s the 10th airman to be tried as a result of a four-month investigation that ended in December 2003.

Marshbank received one of the toughest sentences yet: 15 months of confinement, reduction in rank to E-1 and a bad-conduct discharge.

He was found guilty of attempt to possess cocaine, use of the drug on diverse occasions and distribution of cocaine multiple times.

In a separate court-martial last week, Airman 1st Class Michelle Lewis, assigned to the 31st Aircraft Maintenance Squadron, was found guilty of using cocaine. She was sentenced to reduction in rank to E-1 and a bad-conduct discharge.

Both cases resulted from an investigation by the 31st Security Forces Squadron and Office of Special Investigations Detachment 531 that netted about a dozen suspects. The sting culminated in the detention of a dozen people on base. Some of them lived off base. All were enlisted.

Brig. Gen. Mike Worden, the 31st commander at the time, then ordered a dorm-by-dorm search on base. No more cocaine was found during the search.

Three more airmen are likely to face courts-martial in the next few months as a result of the investigation.