Story highlights A link to a Google Drive folder containing the photos was posted to the private Facebook group "Marines United"

It is not known how many current and former Marines may be involved in potential wrongdoing

(CNN) The Naval Criminal Investigative Service (NCIS) has opened an investigation into the online posting of potentially hundreds of explicit photos of current and former female Marines and other service members, CNN has confirmed.

A private Facebook group called "Marines United" contained a link to a Google Drive folder, where the photos were being stored, a US defense official told CNN. Members on the site solicited others to submit photos of women without their knowledge. The cloud storage folder has been removed at the request of the military, the official said. It was not clear to the Defense Department how many current and former Marines may be involved in potential wrongdoing. A former Marine originally brought the matter to the attention of the Marine Corps last month.

"We are thankful that Thomas Brennan, a Marine veteran, notified the Marine Corps and NCIS about what he witnessed on the 'Marines United' page. It allowed us to take immediate action to have the explicit photos taken down and to prepare to support potential victims. We are exploring what actions should be taken to best address this form of harassment in the future," Marine Corps spokesman Capt. Ryan Alvis said in a statement.

Brennan founded The War Horse, a military news site investigating defense and veterans issues, which first reported the allegations on a separate site, Reveal, run by the Center for Investigative Reporting.

Because of the ongoing investigation, officials would not comment specifically on the case. However, Alvis added that "the Marine Corps is deeply concerned about allegations regarding the derogatory online comments and sharing of salacious photographs in a closed website. This behavior destroys morale, erodes trust, and degrades the individual."

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