A stampede at a U.S.-backed aid distribution center in the Gaza Strip on Wednesday killed at least 20 people waiting for food. The Gaza Humanitarian Foundation said 19 of the victims were trampled, with one person fatally stabbed.

Officials with the aid organization said the melee was caused by agitators in the crowd who gathered at the site on the outskirts of Khan Younis, the largest city in southern Gaza.

“We have credible reason to believe that elements within the crowd — armed and affiliated with Hamas — deliberately fomented the unrest,” the GHF said in a statement. “For the first time since operations began, GHF personnel identified multiple firearms in the crowd, one of which was confiscated.”

The U.N., which has criticized the GHF since it began operating in the Gaza Strip in May, said it recorded more than 670 deaths in the vicinity of the group’s aid distribution sites.

“We’ve been banned from bringing any humanitarian assistance into Gaza for more than four months,” said Juliette Touma, a spokeswoman for the U.N. agency for Palestinian refugees, known as UNRWA. “Medicine and food are going to soon expire if we’re not able to get those supplies to people in Gaza who need it most.”

Officials with the GHF said Wednesday’s incident follows a “deeply troubling pattern” in recent days, including false messages about aid site openings that fuel confusion and disorder. They issued a warning in Arabic late Tuesday for residents of the Palestinian enclave to refer only to official GHF channels for updates on their operations.

“We mourn the lives lost today, and we remain committed to providing humanitarian aid as safely and responsibly as possible,” the GHF said.

• Mike Glenn can be reached at mglenn@washingtontimes.com.