"Looking at the totality of the information we have, we judge that there's a significant possibility that this could have been an explosive device," he said Thursday.
Should that "significant possibility" become reality, suspicion may fall on a variety of terrorist groups active in the region.
Affiliates of both ISIS and al Qaeda have a presence in Egypt. Al Qaeda in the Arabian Peninsula, or AQAP, has a record of disguising sophisticated bombs and getting them on commercial flights.
Even Chechen jihadists, who now have an important role within ISIS in Iraq and Syria, might be suspected of taking part in some way, given their perennial desire to hit Russian targets.
The Russian plane broke apart midair on Saturday. The flight was heading from Sharm el-Sheikh, a popular tourist destination in Egypt, to St. Petersburg, Russia. All 224 people on board died.
A wide range of groups
For now, most attention centers on ISIS' Egyptian affiliate, the Islamic State in Northern Sinai, called ISNS. It has proven itself a durable opponent to the Egyptian state in the past two years, carrying out frequent attacks against the police and army, assassinating officers and judges.
The group has claimed responsibility for bringing down the jet, but Russian and Egyptian officials have dismissed that claim.
ISNS' focus of operations has been the area around al-Arish on the Mediterranean, a long way from Sharm el-Sheikh. But "Wilayat Sinai," as ISNS is called, has previously shown itself able to strike beyond the northern desert. In August, it claimed responsibility for the beheading of a Croatian engineer, Tomislav Salopek, in the western desert on the other side of Cairo, and posted photographic evidence of his killing. (There was, however, some speculation that a criminal gang had abducted Salopek and handed him over to ISNS.)
The Islamic State in Northern Sinai has also shown itself capable of complex operations, including the successful targeting of an Egyptian naval vessel in the Mediterranean with a Russian-made Kornet anti-tank missile, and a multipronged attack in July on the town of Sheikh Zuweid in Sinai that left many soldiers and police dead. The official count was 23; other estimates were higher.
ISNS -- which also uses IEDs and vehicle-borne suicide bombs against Egyptian security forces -- has proved repeatedly that it knows how to handle explosives. It has benefited from the flow of weapons from Libya, where Moammar Gadhafi's arsenals have been raided by a variety of groups and shipped in every direction.
ISNS has not carried out attacks as far south as Sharm el-Sheikh, where security to protect the important tourist resorts is high. But terrorism in Egypt has reached beyond Sinai this year, as far as the capital, Cairo. A huge bomb was detonated outside the Italian consulate in July -- later claimed in the name of the Islamic State. Twelve days previously, Egypt's attorney general was assassinated in a car bomb attack. That attack was claimed by a little known group called the Giza Popular Resistance, evidence that there are other actors in Egypt besides ISNS.
Several crude bomb attacks in February were claimed by similarly obscure groups, who would seem unlikely to have the expertise to get a device onto a commercial plane at the other end of Egypt. Some of these attacks may have been the work of jihadist cells in the Nile Valley, which see themselves as independent actors supportive of ISIS, rather than belonging to the Sinai branch.
According to a recent study by Mokhtar Awad and Samuel Tadros in the Combating Terrorism Center journal, Sentinel,
"New recruits traveled to Sinai to receive weapons and explosives training, while a few others briefly joined the Syrian jihad before returning with urban combat skills and experience."
There is also the growing threat from Islamic State wilayat (or provinces) in neighboring Libya, which the Egyptian air force has occasionally targeted.
Nor is al Qaeda extinct in Egypt (its leader, Ayman al Zawahiri, is Egyptian). A group called Al Mourabitoun declared its allegiance to Zawahiri earlier this year and is suspected of carrying out an attempted suicide attack at the Karnak Temple in Luxor in June. The group is led by a former Egyptian special forces veteran, Hisham Ashmawy.
There is, then, no shortage of jihadist groups within Egypt or neighboring countries. All will have been angered by Russia's intervention in Syria. The question is which of them has the resources and sophistication to penetrate airport security with an explosive device and smuggle it on board an aircraft.
Planes the 'Holy Grail'
Many jihadist groups would have both the motive and desire to attack a passenger airliner. Al Qaeda is the only one with a track record of doing so in recent years, although female Chechen suicide bombers brought down two Russian airliners almost simultaneously in 2004.
The 9/11 attacks demonstrated that for al Qaeda, hijacking and/or blowing up civilian planes was a priority. In 2002, two shoulder-fired anti-aircraft missiles were fired at an Israeli airliner as it took off from Mombasa, Kenya. The plane was not hit.
There followed a variety of plots in Asia and Europe -- all thwarted -- before the emergence of al Qaeda in the Arabian Peninsula and its master bomb-maker, Ibrahim al-Asiri. He was responsible for the "underwear" bomb that threatened a U.S. airliner
during its descent to Detroit on Christmas Day 2009.
Al-Asiri is also thought to have designed more sophisticated devices in 2010 disguised inside printers
and loaded as freight in Sanaa, Yemen, bound for the United States. A tip-off from the Saudi authorities led to the discovery of the bombs, one of which had already been shipped as far as the United Kingdom.
AQAP has repeated its goal of targeting U.S. interests in the Middle East and further afield. Now, Russian President Vladimir Putin's intervention in Syria -- where the Russian air force has targeted al Qaeda affiliate Jabhat al Nusra, among other groups -- may well make Russian targets as much a priority for al Qaeda affiliates.
There is also some evidence of an AQAP presence in or connection with Egypt. A raid by Egyptian security forces in Cairo three years ago led to the recovery of a computer belonging to Muhammad Jamal al Kashef, on which he had addressed messages to al Qaeda leader Ayman al Zawahiri. In one he mentioned he had "received an amount of money from our brothers in Yemen," and talked of his long-standing relationship with AQAP's leadership. Jamal is now in an Egyptian jail.
The choice of a vacation destination such as Sharm el-Sheikh would also appeal to terrorist groups as a high-profile attack on both the income and image of a country ruled by what they would describe as an "apostate regime." Hence the two attacks against tourists in Tunisia this year, both claimed by ISIS-associated groups, as well as attacks in Casablanca (2007) and Marrakesh (2011) in Morocco.
There have also been terror attacks and plots against the tourist industry in Egypt in the last decade, including Sharm el-Sheikh. In July 2005, 88 people were killed by three bombs detonated in Sharm. The Egyptian authorities blamed radicalized Bedouin tribesmen working with Islamist militants for the bombings. Many Bedouin tribes in Sinai complain of neglect and heavy-handed security; some of the younger generation have turned to militant groups, according to human rights groups. Sinai is also infamous for the smuggling of everything from weapons to cigarettes to would-be migrants.
Last year, a suicide bomber attacked a tourist bus in Taba, killing three South Koreans. That attack was claimed by Ansar Beit al Maqdis, which later in 2014 became the Islamic State in North Sinai. And it was a sign that the group could act beyond its north Sinai heartland.
ISNS has also shown a budding interest in targeting the fragile Egyptian economy by killing foreign workers. Before Salopek was killed, an American citizen, William Henderson, was gunned down in an apparent car-jacking. Months later, Ansar Beit al Maqdis published photographs of Henderson's passport and other ID cards, claiming it had killed him.
Should it become clear that the Metrojet flight was brought down by a bomb, there will be no shortage of suspects or motives.
As Tadros and Awad conclude in their CTC study, "The ever entrepreneurial al Qaeda and the 'core' leadership of the Islamic State are unlikely to overlook Egypt -- the fountainhead of Islamism and the most populous Arab country -- when it holds so much promise in advancing both groups' global projects."