KABUL, Afghanistan (AP) — Nine local staffers for Doctors Without Borders were killed and 30 were missing after an explosion near their hospital inhospital-in-Kunduz-hit-by-an-airstrike the northern Afghan city of Kunduz that may have been caused by a U.S. airstrike.

A U.S. Army spokesman says U.S. forces conducted an airstrike on Kunduz that “may have resulted in collateral damage to a nearby medical facility.” He says the incident is under investigation.

Doctors Without Borders said its trauma center “was hit several times during sustained bombing and was very badly damaged.” At the time of the bombing, the hospital had 105 patients and their caretakers, and more than 80 international and Afghan staff, it said.

doctors-without-borders-hospital-airstrike-robertson-00000908-exlarge-teaseAn Afghan Interior Ministry spokesman said 10 to 15 “terrorists” had been hiding in the hospital at the time of the strike. He told reporters “all of the terrorists were killed but we also lost doctors.”

Afghan forces backed by U.S. airstrikes have been fighting to dislodge Taliban insurgents who overran Kunduz on Monday.