NEW YORK (AP) — Several humanitarian aid organizations suspended operations in Gaza on Tuesday after an Israeli airstrike killed seven World Central Kitchen workers.

The nonprofits, including World Central Kitchen, said they now need to determine whether their workers can safely provide aid in the region. According to the United Nations, more than 200 humanitarian aid workers have died since the war began in October.

“We are horrified and heartbroken by the tragic killing of seven innocent humanitarians in Gaza,” said Chris Skopec, executive vice president of global health at Project HOPE, which operates health clinics in Rafah and Deir al-Balah and provides medical supplies and other aid to area hospitals.

The three World Central Kitchen vehicles, hit after loading up with food from a nearby warehouse, were clearly marked and their movements were known to the Israeli military, according to the organization.

Those steps are what humanitarian workers use to try to ensure their safety in the dangerous region, Skopec said. For the World Central Kitchen convoy to still be hit with military fire increased apprehension among aid workers in the region, he said.

“There needs to be accountability,” Skopec said. “The government of Israel needs to be able to give assurances that they consider aid works legitimate actors in Gaza and that international law will be respected. We need to be able to do this critical, life-saving work safely.”

Israeli Prime Minister Benjamin Netanyahu acknowledged that the country’s forces had carried out the “unintended strike … on innocent people.” He said officials were looking into the strike and would work to ensure it did not happen again.

In a briefing Tuesday, White House national security spokesman John Kirby said the United States is concerned the incident could have a chilling effect on other groups carrying out aid operations in the territory.

Anera, a partner of World Central Kitchen and Project HOPE that provides humanitarian aid in the Middle East, also announced Tuesday it would take the “unprecedented step” of pausing its humanitarian operations in Gaza. Since the war began, Anera’s team has provided an average of 150,000 meals daily in Gaza.

“The blatant nature of the attack on WCK’s convoy has proven that aid workers are currently under attack,” said Anera media relations officer Steve Fake. “Our decision to resume aid relies on the safety of our staff.”

The International Medical Corps, which has one of the largest fields hospitals in Rafah with 140 beds said it is “rethinking our process,” including its plans to set up another field hospital in Deir al-Balah.

“It is devastating,” said Dr. Zawar Ali, who has been running the Rafah field hospital and is working to set up the new hospital. “It really is an immense blow to morale. It puts us (in) a very uncertain position in terms of our coordination with the different actors for security.”