A Black Hawk helicopter made a hard landing during combat operations in Afghanistan, injuring four US soldiers, the military said Monday. The incident occurred in southern Uruzgan province on Saturday, US military spokeswoman Sgt. Marina Evans said. A military statement said three of the injured were treated and released while the fourth was in stable condition at a nearby base. The cause of the incident was under investigation and the helicopter was taken to a nearby airfield for repair, it said.