The U.S. military said it was "reviewing" a report Wednesday that one of its airstrikes hit a residential building in Afghanistan.
A local lawmaker told The Associated Press that 13 civilians were killed. NBC News could not independently confirm that account.
American officials confirmed in an email to NBC News that it carried out one strike in the Achin district of Nangarhar province and that it was "aware of some claims of Afghan casualties."
Brig. Gen. Charles Cleveland, U.S. Forces-Afghanistan spokesman, said in the emailed statement that while they military does not "discuss the details of counter-terror operations" it was "currently reviewing all materials related to this strike."
Cleveland said officials were "continuing to look into these allegations and will provide additional information as appropriate." He added that the U.S. military in Afghanistan "takes all allegations of civilian casualties very seriously."
Local lawmaker Esmatullah Shinwari told The Associated Press that an airstrike in Achin had hit a residential building where a crowd had gathered to welcome home a tribal leader returning from the Hajj, an annual Muslim pilgrimage to Saudi Arabia.
Shinwari said 13 people were killed, according to the AP.
Hazrat Hussain Mashreqiwal, the spokesman for the provincial police chief, told the news agency that the airstrike had intended to target ISIS loyalists, who U.S.-backed Afghan forces have been battling in the district for months.
In October, U.S. forces carried out what the charity called a "relentless and brutal aerial attack" on its hospital in the Afghan city of Kunduz, killing at least 42 people.