A visual investigation by ABC News indicates the World Central Kitchen convoy was hit by multiple strikes.
Analyzing ground landmarks in Gaza and satellite imagery, the ABC New Visual Verification team placed the three WCK vehicles, including two armored cars, spread out in different locations over around 1.5 miles, suggesting that the vehicles were hit by at least three separate strikes.
From the position of the cars, the convoy appeared to be traveling south on a key route for humanitarian aid. Photos of one of the vehicles show it with a gaping hole in the roof that was marked with the WCK logo. That vehicle was photographed a half-mile south of the first vehicle, and the third car was found another mile to the south.
Social media posts referring to strikes on civilian vehicles in the area began to appear online at around 10:45 p.m. local time Monday, followed by graphic images of the bodies of the seven aid workers killed.
As information continued to emerge Thursday of the deadly incident, WCK, a foreign-aid organization, called for an independent and international investigation into the killing of seven of its workers in an Israel airstrike in Gaza.
"An independent investigation is the only way to determine the truth of what happened, ensure transparency and accountability for those responsible, and prevent future attacks on humanitarian aid workers," the organization said in a statement.
The seven aid workers were killed Monday night when their three-vehicle convoy, including two armored cars, was struck after leaving the Deir al-Balah warehouse in central Gaza, where the aid workers had helped unload more than 100 tons of humanitarian aid brought to Gaza on the maritime route, according to the statement from WCK, a humanitarian organization dedicated to delivering food aid.
In a phone call Thursday between President Joe Biden and Israeli Prime Minister Benjamin Netanyahu, Biden emphasized that the strikes on humanitarian workers and the overall humanitarian situation are unacceptable, according to a readout of the conversation released by the White House. It was the first call between the two leaders since the strike.
Biden made clear the need for Israel "to announce and implement a series of specific, concrete, and measurable steps to address civilian harm, humanitarian suffering, and the safety of aid workers," according to the readout. The president also told Netanyahu that U.S. policy concerning Gaza "will be determined by our assessment of Israel’s immediate action on these steps," according to the readout.
Biden also underscored that an immediate cease-fire "is essential to stabilize and improve the humanitarian situation and protect innocent civilians."
Following the phone call, Secretary of State Antony Blinken echoed what Biden told Netanyahu, saying American policy in Gaza could change if Israel doesn't heed the president's call to "address civilian harm." He wouldn't detail those potential changes.
"With regard to our policy in Gaza, look, I’ll just say this, if we don't see the changes that we need to see, there'll be changes in our own policy," Blinken told reporters in Brussels.
WCK, which was founded by Chef Jose Andres, described the airstrike that killed the workers as a "military attack that involved multiple strikes" and alleged the organization's vehicles were "targeted."
"All three vehicles were carrying civilians; they were marked as WCK vehicles; and their movements were in full compliance with Israeli authorities, who were aware of their itinerary, route, and humanitarian mission," the non-governmental organization said Thursday.
Asked by reporters Thursday afternoon what concrete steps the U.S. is asking of Israel, John Kirby, White House National Security Council spokesman, said, "What we are looking to see and hope to see here, in coming hours and days, is a dramatic increase in humanitarian assistance getting in, additional crossings opened up, and a reduction in the violence against civilians and certainly aid workers."
WCK said it had asked the U.S., Australian, Canadian and Polish governments to "join us in demanding an independent, third-party investigation into these attacks, including whether they were carried out intentionally or otherwise violated international law."
A senior adviser for Israeli Prime Minister Benjamin Netanyahu said claims that the Israeli strike was intentional were "absurd."
"The last thing we would want in the world is to endanger civilian lives," Ophir Falk, the adviser, told ABC News on Wednesday.
MORE: 'Absurd': Israel rejects claims of targeted attack on World Central Kitchen aid workers in GazaWCK said Thursday that it had asked Israel to preserve all material -- including documents and communications -- that may be relevant to the strike.
Other humanitarian aid groups working in Gaza said Thursday that the strike on the WCK workers is part of a pattern, alleging that many humanitarian aid workers, doctors, nurses and journalists have been deliberately targeted and killed during the Israel-Hamas war.
"The condemnation for the World Central Kitchen incident is right and just, but where is it for every other humanitarian worker, for every other hospital that is destroyed, for every attempt to manipulate the media?" Christopher Lockyear, secretary general of Doctors Without Borders, said at a news conference Thursday. "What happened to WCK is part of a pattern... This is about impunity and total disregard of rules of war."
ABC News' Emmanuelle Saliba, Christopher Looft, Bill Hutchinson, Meredith Deliso, Britt Clennett, Dragana Jovanovic, Jordana Miller and Kuba Kaminski contributed to this story.