Washington: US Director of National Intelligence James Clapper said on Monday he knew of no "direct evidence" that terrorism was to blame for the weekend plane crash of a Russian passenger plane in Egypt.
Speaking at a Washington defense summit, Clapper said it was "unlikely" that the Islamic State group had the capacity to carry out such an attack, but added "I wouldn't rule it out."
"We don't have any direct evidence of any terrorist involvement yet," he said.
The airline has said the Airbus 321 came down due to "external" factors, and that "no technical failures" could account for its apparent break-up in mid-air.
Both Cairo and Moscow have played down a claim from Egypt's Islamic State branch that it brought down the aircraft linking holiday destination Sharm el-Sheikh and Russia on Saturday, killing all 224 people on board.
Investigators are examining all possible causes as they comb the remote crash site in the Sinai peninsula as part of an Egyptian-led probe into the disaster that also involves experts from Russia, Airbus, and Ireland, where the aircraft was registered.