Has Syria used chemical weapons on its own people?

(CBS News) President Obama is in Israel Wednesday night and he took a hard line on two fronts.

He reassured Israelis the United States will do "whatever is necessary" to prevent Iran from getting a nuclear weapon.

And, he said if Syria used chemical weapons in its civil war, as some reports suggested yesterday, that would be a "game changer" which -- officials have suggested in the past -- could cause the United States to take a more direct role in the conflict.

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When reports of an air strike on the Syrian city of Aleppo first came in Tuesday, U.S. intelligence labeled it a "potential" use of chemical weapons. One high level official went further and called it "probable."

That would explain this comment by House Intelligence Committee Chairman Mike Rogers on "CBS This Morning" at left.

"There's at least a high probability they have used, either in most recently or in the past, some amount of chemical weapons," he said.

The initial intelligence assessment was based on the fact that after the air strike in Aleppo, people on the ground claimed they were gassed. Since then, there's been no confirmation chemical weapons were used and experts looking at these videos have not seen symptoms typical of a blister agent like mustard gas or a nerve agent like Sarin. But, as President Obama made clear in his press conference, the case is not closed.

"With respect to chemical weapons, we intend to investigate thoroughly exactly what happened," he said at a joint press conference with Benjamin Netanyahu.

(Watch: Obama says Syria using chemical weapons would be a "game changer")

It's possible these are victims of some other type of agent such as tear gas or an industrial chemical -- nasty stuff, but not a weapon of mass destruction. Still, that would be an ominous step toward chemical weapons -- a probe to test international reaction much as the Assad regime did when it first used aircraft against the opposition, starting with just one flight and gradually increasing the number.

And just as ominous, President Obama said some members of the Syrian regime have actually expressed a willingness to use chemical weapons if that's what it takes to save themselves.