Four U.S. soldiers were injured early Saturday in what appears to be an insider attack in northern Afghanistan, according to both U.S. and Afghan officials. If confirmed, it would mark the second time in a week that members of allied Afghan troops opened fire on American troops.

In a statement, Robert Purtiman, a spokesperson for the U.S. led mission, said that the U.S. military was aware of an incident at Came Shaheen in Mazar-e Sharif. He stated that while there were no U.S. or NATO fatalities, that U.S. soldiers were injured.

In a separate statement, another U.S. official said that four military personnel were wounded. Their conditions were not immediately available. One Afghan soldier was killed in the incident, which remains under investigation.

Camp Shaheen is home to the Afghan army’s 209th Corps and was the site of an attack by the Taliban in April that killed more than 130 Afghan soldiers.

Just last week, three U.S. soldiers were killed and one was wounded in the Achin district of Nanghar Province when an Afghan commando opened fire. The soldiers were assisting operations against the Islamic State at the time.