The United States government said Friday that it was temporarily pausing additional funding for UNRWA, the United Nations humanitarian agency that serves Palestinians, as the organization said it had opened an investigation into allegations from Israel that some of its staff members participated in Hamas' Oct. 7 attack.

On Oct. 7, Hamas militants, designated a terrorist organization by Israel, the U.S. and the European Union, killed around 1,200 people in Israel and kidnapped about 240 others, according to Israeli officials.

UNRWA said it had fired the employees who were accused.

"The Israeli authorities have provided UNRWA with information about the alleged involvement of several UNRWA employees in the horrific attacks on Israel on October 7," Philippe Lazzarini, UNRWA Commissioner-General, said in a statement Friday, according to the Reuters news agency. "To protect the agency's ability to deliver humanitarian assistance, I have taken the decision to immediately terminate the contracts of these staff members and launch an investigation in order to establish the truth without delay."

Lazzarini did not say how many UNRWA employees were accused of participating in the attack, but said "any UNRWA employee who was involved in acts of terror" would be held accountable, and possibly face criminal prosecution. 30,000 people work for UNWRA, according to its website. State Department spokesperson Matthew Miller said 12 UNRWA employees had been accused of participating in the Oct. 7 attack.

Stéphane Dujarric, spokesperson for U.N. Secretary-General Antonio Guterres, said in a social media post that Guterres had been briefed by Lazzarini on the "extremely serious allegations" against the UNRWA staff and that he was "horrified by this news and has asked Mr. Lazzarini to investigate this matter swiftly."

The U.N. chief had urged the termination of the staffers and a referral for criminal prosecution of any UNRWA employees found to have participated in the attack.

The United States, the largest funder of UNRWA, announced that it would temporarily pause further funding for the agency "while we review these allegations and the steps the United Nations is taking to address them."

State Department spokesperson Matthew Miller said in a statement that the U.S. was "extremely troubled" by the allegations and had reached out to the Israeli government about them. He said members of Congress had been briefed.

U.S. Secretary of State Antony Blinken spoke with Guterres Thursday to discuss the allegations and told him "there must be complete accountability for anyone who participated in the heinous attacks," according to Miller's statement.

The U.S. has put its aid for UNRWA on hold previously, under former President Trump in 2018, and the agency has long been accused by Israel of turning a blind eye to Hamas activities in Gaza.

The Biden administration resumed the U.S. funding in 2021, and is now asking Congress for an additional aid package for Israel and the Palestinians.