President Barack Obama says the U.S. is taking "very seriously" the possibility that a bomb caused a Russian plane to crash in Egypt's Sinai Peninsula.
Obama commented Thursday in an interview with a radio station based in Seattle, Washington.
Earlier Thursday, White House spokesman Josh Earnest says the U.S. hasn't determined what brought down the Metrojet flight last Saturday, killing all 224 people onboard.
Earnest said he couldn't discuss what U.S. intelligence officials have learned so far.
He also said the administration is reviewing what steps it can take to enhance security on commercial flights to the United States from certain countries.
U.S. Secretary of State John Kerry reiterated Earnest's remarks while speaking with Egyptian Foreign Minister Sameh Shoukry Thursday. According to a senior U.S. official, Kerry told his Egyptian counterpart that although media outlets have reported on suspected causes of the crash, the U.S. government has yet to make an official determination.
Islamic State militants are taking responsibility for the crash — as a response to Moscow's recent military intervention in Syria against the extremist group. But IS hasn't provided any evidence to support that claim.
On Thursday, Egypt's Aviation Minister Hossam Kamal said they had not found "any evidence or data" that a bomb brought down Flight 7K9268, NBC News reported.
Metrojet has ruled out a pilot error or a technical fault as a possible cause of the crash while Russian authorities have echoed Kamal's comments, noting it was "counterproductive to try to draw conclusions about the causes of the tragedy, (before) the outcome of the investigation," according to a news release from Russia.
However, British and U.S. officials said Wednesday they have information suggesting the plane may have been brought down by a bomb.
British Foreign Secretary Philip Hammond on Wednesday said there was a "significant possibility" the crash was caused by a bomb and grounded all flights to and from Egypt's Sinai Peninsula, stranding thousands of British tourists currently in Sharm el-Sheikh.
U.K. airlines Monarch and Easyjet announced Thursday that they will run flights from the Red Sea resort to London beginning Friday, bringing back stranded British travelers.