(CNN) -- The United States is investigating allegations that some members of the Afghan air force have used their planes to transport drugs, a U.S. military spokesman said Thursday.
Investigators want to know whether the drug-running allegations, first reported in the Wall Street Journal, are linked to the shooting deaths last year of eight U.S. Air Force officers at the airport in the Afghan capital, Kabul.
"The allegations of improper use of AAF aircraft is being looked into," said Lt. Col. Tim Stauffer, referring to the allegations that Afghan air force equipment has been used to illegally ferry drugs and arms.
He said that he was aware of media reports linking this investigation to a shooting at Kabul International Airport in 2011 but that the investigation was ongoing.
A U.S. Air Force investigation into the killing of the eight American officers found that the shooter acted alone.
The exhaustive report describes a shooter who was radicalized and vocally anti-American at times but at other times interacted with American mentors and trainers in his capacity as a pilot.
The Wall Street Journal reported that the majority of the officers killed were involved in an early investigation into the misuse of Afghan planes.
The shooter, Ahmed Gul, was the Afghan officer who coordinated the Afghan air force's cargo movement, the newspaper said.
According to the paper, Western officials say early findings suggest that Afghan air force officials may have been involved in drugs and weapons transporting or at least turned a blind eye to it.
CNN's Nick Paton Walsh contributed to this report.