A bomb planted on a Russian passenger jet exploded directly beneath a 15-year-old girl and a 77-year-old woman, killing them instantly in a crash which claimed 224 lives.
The Daily Mail reports investigators believe the blast went off with the force of more than a kilogram of TNT beneath seats 30A or 31A on the Airbus A321 jet which crashed in the Sinai desert in Egypt on October 31.
Maria Ivleva, 15, and Nadezhda Bashakova, 77, were most likely killed instantly by the blast.
Russian media reports passengers between rows 27 and 32 were also likely killed immediately.
Others on the aircraft may have endured the terror of the crash for much longer, however, as the plane broke apart of plummeted to earth.
Two workers from Egypt’s Sharm el Sheikh International Airport, from which the plane had taken off 23 minutes before the tragedy, were arrested over the downing of Metrojet Flight 9268 last week.
Islamic State has claimed responsibility for the attack and posted images of a bomb built in a pineapple tin to social media.
The group said it "discovered a way to compromise the security at the Sharm el-Sheikh International Airport," without providing further details.
It said it originally planned to bring down a plane from one of the countries participating in the US-led coalition that has been striking it in Syria and Iraq.
It changed the target to a Russian plane after Moscow began launching airstrikes in Syria in September.
Russian and Egyptian authorities initially denied claims a bomb had been responsible for the crash.
Shortly afterwards British investigators said they believed an explosive device had been the cause. Audio from the plane’s blackbox also appeared to reveal a noise which was likely the sound of the detonation.
Investigator Alexander Bortnikov confirmed the attack was unequivocally ‘an act of terrorism’ last week.
"(An) equivalent of up to one 1.5kg of TNT went off during the flight. As a result the plane disintegrated in mid-air, which explains widely scattered fuselage pieces,” he said.
Russian president Vladimir Putin vowed revenge for the attack, which he said was one of the greatest crimes Russia had seen. He offer a $69m reward for information leading to the arrests of those responsible.
"We are not going to wipe tears from our souls and our hearts. This will remain with us forever.
"But this will not prevent us from finding and punishing the criminals. We should be looking for them, no matter how much time passes.
"We need to know them by their names. We will find them, wherever they are, and we will punish them."
Since the attacks Russian fighter jets have reportedly hit more than 400 IS targets in Syria.
The air raids continue as French forces also step up their missions against the terrorists in the wake of the deadly attacks in Paris on November 13.
Suicide bombers and gunmen killed 130 people in the French capital, sparking a strong response from the European nation. French bombers were in the air over the IS stronghold of Raqqa within days.
The two terrorists attacks led world leaders attending last week’s G20 summit to put combating militant extremists in the Middle East high on the agenda. Reports soon emerged that US president Barack Obama and Mr Putin had finally found common ground on their conflicting approaches to Syria.Just days later, China, one of the few global powers to remain on the sidelines amid the growing turmoil spreading from the Middle Eastern country, broke its silence after IS terrorists claimed to have executed one of its citizens, 50-year-old Fan Jinghui.
"The Chinese government strongly condemns this savage act devoid of humanity and will certainly bring the criminals to justice," the Chinese government said in a statement.
"The Chinese government will resolutely oppose all forms of terrorism and resolutely strike at any violent terrorist criminal activities that defy the bottom lines of human culture," it added, noting Beijing would strengthen anti-terrorism co-operation with the international community.