Eighteen midshipmen at the U.S. Naval Academy in Annapolis, Md., have been expelled or resigned following an investigation into cheating on a physics exam in December 2020, officials said Friday.

More than 650 midshipmen took the final exam that month for General Physics I, which was administered through an online platform. The students were given written and verbal instructions that said they could not use outside websites or sources to complete the test, according to a statement from the academy.

Vice Adm. Sean Buck, the academy’s superintendent, initiated an investigation after learning midshipmen may have used outside sources, including other websites, during the exam, officials said. Academy leaders were also made aware that some midshipmen used an anonymous chat platform to discuss the exam after they finished.

“Character development is an ongoing process and midshipmen must make the choice to live honorably each day and earn the trust that comes with a commission in the Navy or Marine Corps,” Buck said in a statement Friday. “This incident demonstrates that we must place an increased focus on character and integrity within the entire brigade.”

Despite efforts by the physics department to prevent cheating - including requiring midshipmen to submit their calculations from the test on a sheet of paper - 105 midshipmen were identified to have probably accessed unauthorized resources during the test.

Naval officials withheld the names of those involved but said 61% of them are varsity athletes and 83% are men. Five of the midshipmen were at the top quartile of their class, while 66 were at the bottom. The majority of the students were sophomores.

“The biggest vulnerability identified was inadequate proctoring,” officials said in the statement. The academy now “strongly advises” instructors to use paper-based, in-person tests and use browser security programs during online exams.

Eighty-two midshipmen were found to have violated the school’s honor code, and were retained in the brigade with sanctions and entered into a five-month remediation program, according to officials. Four other students were found not in violation and one is awaiting adjudication by the Brigade Honor Board. As the investigation proceeded, some students chose to submit resignations while others were expelled.

The entire brigade of midshipmen conducted a day-long conference in April that included “intensive training and discussions on honor,” officials said, adding “there will be a renewed focus on character and professional development throughout this academic year.”

Rep. C.A. Dutch Ruppersberger (D-Md.), who chairs the Naval Academy’s board of visitors, issued a statement supporting the findings of the investigation. The board oversees matters related to discipline, financial affairs and curriculum at the academy.

“The Academy’s Honor Concept is clear and anyone who violates it must be held accountable,” Ruppersberger said Friday. “Midshipmen must earn the privilege to study at one of our nation’s most prestigious institutions and their character and conduct must be worthy at all times.”

Students who attend the Naval Academy receive a full scholarship in return for five years of active duty service upon graduation. Midshipmen who are discharged or resign before their junior year are not required to repay the academy for their education or be required to serve in the enlisted ranks.

The Naval Academy first announced its investigation in December, around the time the U.S. Military Academy at West Point accused 73 cadets of cheating on a freshman calculus exam. The elite academy allowed many cadets to repeat a year, sparking a backlash from alumni who accused the school of being too lenient.

This is not the first time the Naval Academy has been tarnished by a cheating scandal. In 1994, then-Navy Secretary John H. Dalton ordered 24 midshipmen expelled for cheating on an electrical engineering exam. Some students were accused of buying and selling copies of the exam, while others were charged with writing formulas on index cards used during the test.