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Story highlights

Homeland Security Secretary Jeh Johnson said U.S. aviation officials "make adjustments all the time"

Johnson on Friday announced security enhancements that include expanded screening to all items on aircraft and airport assessments alongside foreign countries

(CNN) —  

Homeland Security Secretary Jeh Johnson is seeking to reassure the American public that security officials are evaluating terror threats in the wake of last week’s crash of a Russian plane over the Sinai Peninsula.

“I want people to know that their aviation security officials, working on their behalf, are continually evaluating threats, potential threats, and we make adjustments all the time based on what we see,” Johnson told CNN’s Barbara Starr in an interview that aired Saturday.

RELATED: Investigator: Noise heard in final second of Metrojet Flight 9268

Johnson on Friday announced security enhancements that include expanded screening to all items on aircraft and airport assessments alongside foreign countries.

“This is why we determined to take precautionary interim steps while this investigation is still ongoing. ISIL is out there now, active in a lot of different areas, and so while this investigation is pending – and cause we have this group claiming responsibility – we believe it’s significant to do these things on an interim basis and to tell the public that we’ve done this,” Johnson told Starr.

“We want the public to know that our aviation security officials are very much focused on this,” he added. “We’re continually evaluating whether more or less is necessary.”

On Saturday, the head of Egypt’s investigation said a noise was heard in the final second of the cockpit voice recording on Metrojet Flight 9268 as it ascended on autopilot before apparently breaking up about 23 minutes after takeoff. All 224 people aboard were killed.

While U.S. and UK officials have said there may have been a bomb aboard the jet, the chief of the investigation said authorities have not reached any conclusion as to what brought down the flight.

“All the scenarios are out on the table,” Ayman al-Muqaddam told reporters. “We don’t know what happened exactly.”

Signs pointing to ISIS as the culprit, a U.S. official said, came from monitoring the terrorist group’s internal messages. Those messages are separate from public ISIS claims of responsibility, the official said.