"I am learning about aspects of this as I question our folks in Afghanistan," Pentagon spokesperson Bryan Whitman told the regular Pentagon news briefing.
"If I find something that is inconsistent with Defense Department values and policies, you can be sure I will address it," he added.
The probe comes three days after The Stars & Stripes first uncovered the screening of reporters on Monday.
According to the newspaper, the U.S. military hired The Rendon Group, a private public-relations company to screen the journalists.
Under such a screening system, reporters who request to be "embedded" into U.S. military units in Afghanistan will be rated as "positive", "negative" or "neutral" towards U.S. strategy.
When the practice was first reported, the U.S. military denied it.
However, as more evidence popped up and facing growing protests from journalists, the military finally acknowledged it and agreed to launch an informal investigation into the issue.
Published by Mike Hitchen,
Putting principles before profits
Afghanistan Media Censorship Rendon Group
Putting principles before profits
Afghanistan Media Censorship Rendon Group