There’s no immediate indication that the crash of a Russian passenger jet in Egypt was the result of terrorism, although the U.S. doesn’t rule out the ability of Islamic State to shoot down airliners in that part of the world, Director of National Intelligence James Clapper said Monday.

“We don’t have any direct evidence of any terrorist involvement yet,” Clapper said in public remarks at the Defense One Summit in Washington. He said the U.S. is still waiting to learn more about the investigation.

The Metrojet Airbus Group SE A321 plummeted Saturday into a remote area of Egypt’s Sinai peninsula 23 minutes after leaving the Red Sea resort of Sharm el-Sheikh on a flight to St. Petersburg, killing all 224 people aboard.

Wreckage was found in an area about 5 miles long by 2.5 miles wide, suggesting the aircraft broke up at high altitude, Alexander Neradko, the head of the Russian Federal Aviation Authority, said in an interview with Rossiya-24 state television.

Investigators will be looking at causes of similar crashes such as bombs, missiles, on-board explosions and structural failures.

So far, neither Egyptian nor Russian officials have said there’s any evidence of a bomb.

External Impact

An official with the airline told reporters Monday that an external impact probably caused structural damage leading to the crash.

“It could have been anything,” Alexander Smirnov, deputy general director for Kogalymavia, known by the Metrojet brand, told reporters at a briefing in Moscow Monday, declining to comment on a possible terrorist attack. “The only reasonable explanation may be a mechanical impact on the aircraft.”

While the Islamic State’s Sinai affiliate claimed responsibility for shooting the plane down, Egyptian and Russian officials said those claims weren’t credible. Only the most sophisticated ground-based missiles can reach 31,000 feet, the cruising altitude at which the Metrojet encountered problems and began to fall.

The Islamic State, also known as ISIL, has “a very aggressive” presence in the Sinai Peninsula, Clapper said. When asked if the extremist group could shoot down an airplane, Clapper said: “It’s unlikely but I wouldn’t rule it out.”

This article was written by Chris Strohm from Bloomberg and was legally licensed through the NewsCred publisher network.

Photo Credit: Egyptian soldiers collect personal belongings of plane crash victims at the crash site of a passenger plane bound for St. Petersburg in Russia that crashed in Hassana, Egypt's Sinai Peninsula. Russian Ministry for Emergency Situations / Associated Press