KABUL, Afghanistan (KGO) -- NATO says an explosion inside Bagram Airfield, a large U.S. base north of Kabul, has caused casualties.
The statement issued by Operation Resolute Support says the blast happened early Saturday and that "force protection and medical teams are responding to the situation."
ABC7 News has learned that one of the victims was from Stockton. The Department of Defense named 30-year-old Sergeant John Perry as one of the victims.
He was killed Saturday in the the blast, which killed three other Americans including another service member and contractors.
Sixteen other U.S. service members and one Polish soldier were injured.
The Taliban is claiming responsibility.
The Associated Press contributed to this report.