Updated

At least 31 female trainees have been identified as victims in a widening sex scandal targeting a dozen instructors at Lackland Air Force Base in Texas, the Air Force revealed Thursday, providing new details in an investigation that has rocked the service's training command.

Six of the 12 instructors under investigation for misconduct face charges ranging from rape to adultery. A senior Air Force commander said nine of those instructors were in the same squadron, briefing reporters at the Pentagon at the same time that one of the accused appeared in a Lackland courtroom.

Air Force Staff Sgt. Craig LeBlanc, who is charged with aggravated assault and obstruction of justice, allegedly bragged about "getting laid" by a trainee in a supply closet, one of his fellow airmen testified at an evidentiary hearing Thursday.

"I was speechless. I didn't understand," said Staff Sgt. Christopher Beck, according to the San Antonio Express-News.

Gen. Edward Rice, commander of the Air Education and Training Command, said the Air Force believes the misconduct is not endemic to the nine training squadrons. He says the sexual misconduct apparently began in 2009 but that the first woman came forward only a year ago.

Those first allegations were levied against Staff Sgt. Luis Walker, who faces the most serious charges and is scheduled to be court-martialed next month. Walker is charged with 28 counts, including rape, aggravated sexual contact and multiple counts of aggravated sexual assault. He has not yet entered a plea.

The majority of the instructors under investigation were in the 331st Training Squadron, whose commander was relived from his post last week. Rice said Lt. Col. Mike Paquette, who has not been accused of misconduct, was relieved because of the "unacceptable level" of misbehavior in his unit.

"In my assessment to this point, it is not an issue of an endemic problem throughout basic military training," Rice said. "It is more localized, and we are doing a very intensive investigation on that squadron to find out what exactly happened and why."

Lackland is where every American airman reports for basic training -- about 35,000 a year. About one in five are female, pushed through eight weeks of basic training by a flight of instructors that are about 90 percent male.

As the allegations of misconduct mounted, the Air Force in March took the almost unprecedented step of shutting down training for an entire day and interviewing about 5,900 trainees. Rice said Thursday the Air Force received "very little" negative comments about instructors.

Rice said that to his knowledge, all of the 31 female victims identified by investigators are still in the Air Force.

Lackland has about 475 instructors, which is about 85 percent of what the Air Force would consider being fully staffed. Col. Glenn Palmer, who is commander of the entire 737th training wing at Lackland, has said that applicant standards have not been lowered in order to attract more qualified instructors.

The job is among the most demanding on base. Instructors work longer hours than most for four years, at the expense of family and personal time. A smartphone app the Air Force recently launched to help recruit instructors includes a page of frequently asked questions, the first of which is whether the divorce rate among instructors really is higher.

Rice defended the screening process for instructors but said it will still be re-examined. Only 11 percent of instructors are female.

"I will look at whether or not we need to both hire more female (instructors) and whether or not we need to adjust our process to have only female (instructors) over female sites," Rice said.

LeBlanc's hearing Thursday was to determine whether there is enough evidence to warrant a court-martial. Walker's court-martial is scheduled to begin July 16 and his attorneys have declined comment.

On June 28, Congresswoman Jackie Speier implored Congress to act to end the epidemic of rape and sexual assault in the military.

"We need to know from the top that the phrase, zero tolerance for sexual assault in the military, is a fact, not a talking point," she said.

At a June 29 Pentagon press briefing, Secretary of Defense Leon Panetta said he was concerned about the allegations and called the young recruits, "very vulnerable."

"I take sexual assault allegations very seriously," he said. "We have to maintain strict discipline.  We have put steps together on how to deal with this."

The Associated Press contributed to this report.