Reviews come amid increased Taliban attacks and shortfalls in Nato-led forces.
One fuel tanker was reportedly set on fire and a USPI vehicle was taken. Colonel Saydo Khan, a police official, said reinforcements had been sent to the area and were fighting the attackers in a nearby village.
Thousands of people work for Texas-based USPI in Afghanistan.
More than 6,300 people, mostly Taliban or al-Qaeda fighters, have been killed in violence in Afghanistan this year, according to an Associated Press news agency count based on official figures.