The top U.S. diplomat Antony Blinken said he could not verify whether Israel used weapons sent by the U.S. in its latest massacre in Rafah, which killed dozens of civilians seeking refuge in a camp for the displaced in an area designated as a safe zone in Gaza.

Blinken told reporters during a visit to Moldova that what weapons were used and how they were used would have to be the object of an investigation into the attack.

However, a report and analysis by CNN, prepared with insight from four explosives experts, noted that U.S.-made munitions were used in the attack.

"In video shared on social media, which CNN geolocated to the same scene by matching details including the camp’s entrance sign and the tiles on the ground, the tail of a US-made GBU-39 small diameter bomb (SDB) is visible, according to four explosive weapons experts who reviewed the video for CNN," the report said.

Explosive weapons expert Chris Cobb-Smith told the U.S.-based media outlet that the bomb, designed to result in low collateral damage, is manufactured by Boeing. Three other experts also confirmed that the bomb was a U.S.-made GBU-39 bomb.

The U.S., which has been criticized for its unwavering support of Israel's massacres in Gaza, said Rafah killings did not "cross red line" and would not change its policy.

Meanwhile, Blinken also said that Israel should immediately investigate the Rafah incident that killed and injured around 300 people.

"The incident in Rafah was horrific. I don't think anyone who has seen the images cannot be deeply affected by them on a basic human level. We have been very clear with Israel on the imperative in this instance and in other instances to immediately investigate and determine exactly what happened and why it happened. If accountability is necessary, make sure there is accountability," said Blinken.

Blinken also said that incidents similar to the recent deaths in Rafah highlight the urgent need to develop a post-war plan in the Gaza Strip.

"What weapons were used or how they were used in Rafah should be a product of a deliberate, but also fast, investigation... We see that limited, focused target attacks are designed to deal with terrorists who killed innocent civilians... Even those kinds of operations can have terrible, horrible unattended consequences.

"It is very important at this moment after Israel has real success in helping to destroy Hamas' capacity to repeat Oct. 7. It has to ask for a plan in Gaza... In the absence of a plan, how does that stack up against some of the unintended but horrifical coincidences of military action in a place where people you are going after are so closely embedded with civilians?" added Blinken.

According to Blinken, this underscores the importance of having a plan.

A May 26 Israeli strike on a tent camp housing displaced Palestinians in Rafah killed and injured around 300 people, drawing vehement condemnation from around the world.

Israel is accused of genocide at the International Court of Justice, which in its latest ruling ordered Tel Aviv to immediately halt its operation in Rafah, where more than 1 million Palestinians had sought refuge from the war before it was invaded on May 6.