A "full investigation" is being carried out into a deadly bombing at a hospital in the Afghan city of Kunduz, US Defense Secretary Ashton Carter said Saturday, amid wide speculation that the incident was the result of a US air strike.

Carter said that "US forces in support of Afghan Security Forces were operating nearby, as were Taliban fighters," and that a "full investigation into the tragic incident is under way." The bombing killed 16 people, including nine staff.