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The intercepts were part of an immediate review of all intelligence in the hours after the attack to confirm responsibility for the use of chemical weapons in an attack in northwestern Syria, which killed at least 70 people, CNN reports.

U.S. officials have said that there is "no doubt" that Syrian President Bashar al-Assad is responsible for the attack.The US did not know prior to the attack it was going to happen, the official emphasized. The US scoops up such a large volume of communications intercepts in areas like Syria and Iraq, the material often is not processed unless there is a particular event that requires analysts to go back and look for supporting intelligence material.

Read alsoUSA Today: Trump: U.S.-Russian relations 'may be at an all-time low'So far there are no intelligence intercepts that have been found directly confirming that Russian military or intelligence officials communicated about the attack. The official said the likelihood is the Russians are more careful in their communications to avoid being intercepted.

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The Russian and Syrian governments have both denied involvement in the chemical attack.

Read alsoTillerson: Russia must choose between Assad and U.S. – mediaFor now, the most specific evidence of Russian involvement remains a Russian drone that flew over the hospital that was treating people injured in the attack, according to the U.S. military official. The US has specific intelligence showing it was a Russian drone. While the drone operator may not have known why the aerial vehicle was flying in the area, it was a Russian-controlled asset.