SAN ANTONIO (June 25, 2012)--A widening sex scandal is rocking Lackland Air Force Base in San Antonio, which is one of the nation's busiest military training centers.

Four male instructors at Lackland are charged with having sex with, and in one case raping, female trainees.

Charges against others are possible.

The most serious accusations surround an Air Force staff sergeant who is charged with rape and aggravated sexual assault.

He is scheduled to face a court-martial in July.

The other three defendants are charged with lesser crimes ranging from sexual misconduct to adultery.

The defendants are all instructors whose job it is to turn raw recruits into airmen in eight weeks of basic training.

A two-star general is now investigating alongside a separate criminal probe.