World leaders are vowing to investigate the latest allegations of a chemical weapons attack in Syria. Both sides of the Syrian conflict accused the other of responsibility for an incident in Aleppo, although no evidence has emerged chemical weapons were involved. On Wednesday, both rebels and the Syrian government called for a U.N. probe. Speaking during his visit to Israel, President Obama expressed caution about the chemical weapons claims but renewed his call for the ouster of Syrian President Bashar al-Assad.

President Obama: “We intend to investigate thoroughly exactly what happened. Obviously, in Syria right now you’ve got a war zone. We have information that’s filtered out. But we have to make sure that we know exactly what happened, what was the nature of the incident, what can we document, what can we prove. The Assad regime has lost all credibility and legitimacy. And I think Assad must go, and I believe he will go.”