KABUL, Afghanistan — Officials in Afghanistan said on Sunday they were investigating claims that at least nine civilians, including six children, had been killed when Afghan and coalition forces blew up a Taliban weapons depot in southern Helmand Province.

Omar Zwak, a spokesman for the governor of Helmand, said troops on a joint military operation in the Malgir area of Gereshk district, just outside the provincial capital of Lashkar Gah, had found the cache of munitions late on Saturday.

“They set up explosives to detonate the cache, and it damaged the house where the civilians were staying,” Mr. Zwak said.

Capt. Bill Salvin, a spokesman for the coalition in Afghanistan, said on Sunday: “We have seen the reports of civilian casualties in southern Helmand last night. We take all allegations of civilian casualties seriously, and we will convene an inquiry into this allegation.”