WASHINGTON -- Children of service members are sexually assaulted hundreds of times each year, according to data the Defense Department provided exclusively to The Associated Press.

The abuse of military dependents is committed most often by male enlisted troops, the data show, followed by family members.

The figures offer greater insight into the sexual abuse of children committed by service members, a problem of uncertain scale due to a lack of transparency into the military's legal proceedings. With more than 1 million military dependents, the number of cases appears statistically small. But for a profession that prides itself on honor and discipline, any episodes of abuse cast a pall.

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Those numbers fall well-short of a full picture.

Ages of the offenders and victims, locations of the incidents and the branches of service that received the report of sexual abuse were omitted. The Defense Department said in a statement that "information that could unintentionally uniquely identify victims was withheld from release to eliminate possible 're-victimization' of the innocent."

It's also unclear how many of the incidents resulted in legal action. The cases represent substantiated occurrences of child sexual abuse reported to the Defense Department's Family Advocacy Program, which does not track judicial proceedings, the department said.

An AP investigation published in November found more inmates are in military prisons for child sex crimes than for any other offense. But the military's opaque justice system keeps the public from knowing the full extent of their crimes or how much time they spend behind bars.

Responding to AP's findings, three Democratic senators have urged Defense Secretary Ash Carter to lift what they called the military justice system's "cloak of secrecy" and make records from sex crimes trials readily accessible.

The senators also raised another concern: Cases involving children are not included in the Defense Department's annual report to Congress on sexual assaults, which focuses primarily on adult-on-adult incidents, they said. The senators - Barbara Boxer of California, Kirsten Gillibrand of New York and Mazie Hirono of Hawaii - told Carter in a Dec. 8 letter they are concerned the department may be underestimating how many sexual assaults are occurring in the military.

There were at least 1,584 substantiated cases of military dependents being sexually abused between fiscal years 2010 and 2014, according to the data. Enlisted service members sexually abused children in 840 cases. Family members of the victims accounted for the second largest category with 332 cases.

Most of the enlisted offenders were males whose ranks ranged between E-4 and E-6. In the Marine Corps and Army, for example, those troops are corporals, sergeants and staff sergeants. Officers were involved in 49 of the cases. The victims were overwhelmingly female.

Kathy Robertson, manager of the Family Advocacy Program, said in an emailed response to questions that the incident rates reflect the U.S. military's demographics. Most of the cases involve the E-4 and E-6 ranks because they are the largest number of active-duty personnel and the largest number of parents in the military, she said.

Duplications in the data indicate as many as 160 additional cases of sexual abuse could have occurred during the 2010 to 2014 period, involving a child who was victimized multiple times or a repeat abuser. The figures also account only for cases involving military dependents, the only child victims the department tracks.