Shepard Smith reported this afternoon that there is no conclusive evidence that a bomb took down a Russian passenger plane in Egypt, according to a U.S. intelligence source.

U.S. and British intelligence authorities had previously been saying that a bomb was likely responsible for Saturday's crash, killing 224 people in the Sinai Peninsula.

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Shep reported that the source told Fox News that the investigators have not found any bomb residue on the wreckage or the victims.

Russian and Egyptian officials have said it is simply too early to determine what led to the crash. The White House has said it cannot rule out any possible cause for the crash, including a terror attack, because there's not enough information at this time.

Shep said the Obama administration is looking at ways to step up security on flights headed to the U.S. from overseas airports. Meantime, the U.K. has grounded all flights to and from the Sinai Peninsula.

Watch the "Shepard Smith Reporting" clip above.

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