WASHINGTON — After weeks of revelations about U.S. military operations in the African country of Niger, another operation is coming to light in the neighboring country of Mali. Another American soldier is dead, only this time it's a homicide, CBS News national security correspondent David Martin reports.

Army Green Beret Staff Sgt. Logan Melgar, 34, died last June in a house he shared with the two Navy SEALs in the capital of Mali. An autopsy ruled his death a homicide, reportedly by asphyxiation.

A law enforcement source said the two Navy SEALs had been involved in an argument with him and are now under investigation by the Naval Criminal Investigative Service.

Get Breaking News Delivered to Your Inbox

After the incident, the two unidentified SEALs were flown out of Mali and placed on administrative leave, The New York Times reported. Melgar and several other Special Operations forces were assigned to the West African nation to help with training and counterterrorism missions, the newspaper adds.

Neither the Pentagon nor the U.S. Africa Command announced Melgar's death, apparently because it would reveal the presence of special operations forces in Mali. Melgar was a member of the same special forces group as the four Americans who were killed while on patrol in the neighboring country of Niger earlier this month.

The Islamic State of Iraq and Syria (ISIS) fighters who ambushed and killed the four soldiers were based in Mali and escaped back across the border.

A Texas native, Melgar was honored at his high school's homecoming football game earlier this month.

The Pentagon is still struggling to explain the sequence of events which led to the deaths of the four soldiers in Niger.

Now it must explain the death of Melgar, as well as what American special operations forces are doing in Mali.