Army officials confirmed Tuesday that more charges have been added in a rapidly widening military sexual assault investigation, with sources familiar with the case telling CBS News that at least 39 alleged victims, including former patients of a military doctor, have now accused the physician of improper touching.

The physician, Maj. Michael Stockin, is at the center of what some experts say could grow to become one of the largest sexual assault cases in military history. Stockin has proclaimed his innocence. 

Military officials say the investigation remains ongoing and it is unclear if additional victims will come forward or be added to the current charges. 

"The general nature of the charges include abusive sexual contact and indecent viewing in violation of the Uniform Code of Military Justice," said I Corps spokesperson Lt. Col. Jennifer J. Bocanegra, noting in a statement that the accused is presumed innocent until proven guilty.

The Army says that additional court-martial charges were added to Stockin's case on Oct. 17. CBS News has learned that the new set of sexual assault claims includes an additional 17 alleged victims. 

"The Defense Team is aware that 17 alleged victims have been added to the charge sheet in this case," said Robert Capovilla, an attorney for Stockin, in a statement noting that the case is still at an early stage. "In the interim, we fully expect that the United States Army will honor Major Stockin's constitutional right to a fair trial. Rest assured that our dedicated Defense Team will thoroughly investigate every single allegation that has been made against our client, and we are confident that the truth will come out in the courtroom."

In August, the Washington Post first reported that charges were expected in the case and later that charges were filed related to at least 23 alleged victims. 

The Army's investigation into Stockin appears to have begun in 2022. Bocanegra added that the Army does not comment on ongoing investigations. 

Stockin, an anesthesiologist at Madigan Army Medical Center based on Joint Base Lewis-McChord, in Washington state, has been suspended from patient care. He has not been detained and a preliminary hearing is scheduled in the case for Nov. 9. 

CBS News has spoken with four of Stockin's accusers who were former patients and say they have been informed by prosecutors that their reports are included in the formal charges. All spoke on the condition they not be identified because of the nature of the ongoing case. They each described a similar pattern. During appointments at the center's pain management clinic, Stockin, when left unchaperoned, would perform nerve sensory examinations and ask patients to drop their trousers and proceed to examine their lower body and touch them inappropriately, the four former patients alleged. 

One alleged victim who was recently informed his charges had been added told CBS News he welcomed the military's action, but questions whether the Army has provided all potential victims "a path toward justice."

The Army has declined to make charging documents publicly available, but redacted versions reviewed by CBS News show that the allegations against Stockin include the claim that he covered up misconduct by falsely representing that it had a "medical purpose."

Stockin has served in the Army since 2013 and has been stationed at Madigan since July 2019. It is unclear whether allegations against him are limited to his time at Madigan, or extend to any of Stockin's previous assignments. He has also served at Walter Reed National Military Medical Center in Bethesda, Maryland, and Tripler Army Medical Center in Honolulu, Hawaii. 

Despite recent policy changes and efforts to curb the prevalence of sexual assault, the latest Pentagon report shows that the number of incidents has continued to grow. In the Pentagon's most recent confidential survey, 16,620 male servicemembers reported experiencing unwanted sexual contact in 2021, however during that year only 960 male servicemembers reported those assaults. The number of reports by male victims increased by 33 reports in 2022. In total, there were 8,942 reports of sexual assault last year involving service members. Some survivors have told CBS News they believe there remains a stigma surrounding reporting sexual assault or harassment in the military.

At least two accusers, referred to only as John Doe 1 and John Doe 2, have filed civil claims under the Federal Torts Claims Act (FTCA) against the Army and the Department of Defense for negligence in hiring and retaining Stockin, and for failing to protect them from sexual abuse.

Ryan Guilds, an attorney representing several alleged victims in Stockin's criminal matter, says while he supports prosecutors' efforts to seek justice in this case, the military's handling of this matter, including the initial identification of victims, has been "haphazard."

"Countless unforced errors and lack of communication serve to reinforce a message of ambivalence toward the men who are now struggling to come to grips with the idea that they were assaulted," Guilds said. "I am deeply concerned there are soldier victims out there suffering alone."