HOUSTON - The number of instructors at a US Air Force training center under investigation for sex charges has increased from 12 to 15, officials said Thursday.

Officials declined to name the three new instructors being investigated in the widening sex scandal at Lackland Air Force in San Antonio, Texas, according to CBS news.

Meanwhile, the number of alleged victims has also increased. The numbers of both the alleged instructors and the victims could continue to grow, according to the report.

"There may be others as we continue the investigation," said Brent Boller, a spokesman for Joint Base San Antonio, which operates Lackland Air Force base.

Last week, ?a military jury at Lackland found Sgt. Luis Walker guilty on charges that included rape, aggravated sexual contact and multiple counts of aggravated sexual assault. Walker was sentenced to 20 years in prison.

Walker is among the 15 trainers investigated in the sex scandal the rocked Lackland Air Force base, one of the country's busiest military training centers.

The alleged crimes of Walker occurred between October 2010 and June 2011, the Air Force said.

Military officials say the initial flirtations Walker directed at the women he trained at the base grew into something more sinister: threats and intimidation that eventually led to rape.

Walker is the first to stand trial in the sex scandal.

Six of the 15 instructors being investigated have been charged.

Another trainer, Vega-Maldonado, who admitted in June to having sex with a female trainee, was given 90 days of confinement as part of a plea deal.

Courts-martial have been set for four other trainers, according to media reports.