Almost a week after the crash of EgyptAir flight MS804 in the Mediterranean, the lack of any real progress in the investigation has continued to fuel speculation that terrorism was to blame, even though there have been no claims of responsibility.
Egyptian authorities were forced on Tuesday to deny reports that human remains retrieved from the sea in the area where the aircraft went down, killing all 66 passengers and crew, pointed to an explosion onboard.
That followed confirmation over the weekend that data streamed from the Airbus A320 showed that smoke alarms were triggered on the plane in the last few minutes before it disappeared from radar in the early hours of Thursday morning.
One of the alarms was in the avionics bay, below the cockpit, which houses most of the aircraft’s vital electronic equipment. The sequence of events suggested the crew had fought a losing battle against an onboard fire for several minutes rather than succumbing to a catastrophic break-up caused by a bomb.
But French air crash investigators, who are involved in the inquiry, said the smoke alarms did not prove there was a fire onboard. They said that monitors can be triggered by air condensing rapidly inside the aircraft following a sudden depressurisation of the aircraft, caused by a catastrophic structural failure.
Ron Lindsay, an aviation security specialist with Gates Aviation, said forensic scientists can test the human remains for explosive residue, which can be detected on human tissue or clothing that has been immersed in water for up to a week.
“You may be able to tell that from either body parts or clothing, dependent on how close they might have been to the detonation,” he said.
Daveed Gartenstein-Ross, a terrorism expert at Georgetown University, said it was too early to jump to conclusions about the cause of the crash just because no one had yet claimed responsibility.
He pointed out that Isis, or other groups, could have decided to stay quiet if they thought they might be able to use the same method again, or if their operatives were at risk of arrest.
This is in stark contrast to last October’s bombing of the Russian Metrojet aircraft over Egypt’s Sinai desert, which killed all 224 passengers and was claimed by the Egyptian branch of Isis within hours.
An audio statement by Isis spokesman Abu Mohammed al-Adnani released over the weekend failed to make any mention of the EgyptAir crash.
Al-Qaeda would have even more reason to hold back from claiming responsibility, Mr Gartenstein-Ross said. It took a year after the 7/7 attacks in London before the group claimed responsibility. “If it was al-Qaeda, then there are clear reasons why they would wait,” he said. “Al-Qaeda does not want to return to the centre of the radar.”
US officials said there was not yet any definitive evidence from satellites or other intelligence to suggest a terrorist attack. Jeh Johnson, the US homeland security secretary, said it was possible that mechanical failure, rather than terrorism, was the cause of the crash.
“I suspect we’ll know over the coming days, but we just don’t know [the cause] yet,” he said. “At this point, we do not rule out an act of terrorism, but there are other possibilities.”
But security services are worried. In a paper published on Monday, Robert Liscouski, a former senior official at the department of Homeland Security, and William McGann, who runs IMplant Sciences, which makes explosive detection equipment, highlighted the bombing in February of a Somali passenger jet.
The aircraft was forced to make an emergency landing after a bomb left a gaping hole in the side of the Airbus A321. The device, which was built into a laptop computer and claimed by al-Shabaab, the Somalian militant group, has been “a wake-up call for security agencies and those working in the field of explosive detection”, they wrote, adding: “There is a high-stakes contest between terrorists developing new techniques to try to beat airport security and the security officials and technologists working to keep bombs off planes.”
Egyptian authorities have said they are keeping an open mind on the cause of the crash. Ahmed Adel, vice-chairman of EgyptAir, told CNN on Tuesday that the data from the aircraft showing the smoke alarms were triggered was “just one piece of the puzzle”.
He said finding the cockpit voice and flight data recorders, the so-called black box, would be crucial but joined others in warning that the search was challenging as it is spread over a 14,000 square km area — larger than the size of the US state of Connecticut.