Both volunteers in a study to see if women could become Marine ground combat leaders have dropped out of the rigorous Infantry Officer Course, with the second failing because of a medical reason late last week, the Marine Corps Times reported.

A second lieutenant was unable to complete the required training and left the program on Friday because of unreported medical reasons, the newspaper reported on its website. It was unknown if she became ill or injured or had other medical issues.

Inquiries from NBC News into her condition were not immediately returned by the Marine Corps.

The other female volunteer, who was also a second lieutenant, was unable to complete the introductory endurance test and dropped out – along with nearly 30 men – on Sept. 28. The program, run at the Marine base at Quantico, Va., is considered the toughest course in the Marine Corps.

Women in the infantry? Forget about it, says female Marine officer

The Marine Corps officer who left the course on Friday issued a statement through the Marine Corps public affairs unit: "I want to try to open up a door, maybe, for women after me. I don’t know how far it will open, but I’m hoping to make a difference for women down the road."

A long debate over changing roles of women in the military reached a turning point in 2011 when Congress directed the Pentagon to take a hard look at policies that restrict female service members from serving in some roles. The Defense Department relaxed some restrictions in February, moving women closer to combat, but a fuller review of combat jobs is under way.

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The Marine Corps’ admission of female officers to the grueling 13-week infantry course is part of an effort to gather research on what jobs would be open to women. It was the first time women had been admitted to the program.

Besides the infantry program, the Corps is evaluating numerous jobs that normally are closed to women. Those jobs include billets in artillery and tank units, as well as others.

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