New evidence has strengthened theories that a bomb caused the destruction of Metrojet Flight 9268 last Saturday.

AFP reports an analysis of the crashed Airbus A321's black boxes point to a potential terrorist attack using an explosive device.

An unidentified source said the plane was flying normally until there was "a very sudden explosive decompression" 24 minutes after takeoff.

Another source said the plane had a sudden and violent descent.

A group of Islamic State sympathizers took credit for the crash over social media, saying the attack was revenge for Russian air strikes conducted in Syria. However, Russian and Egyptian officials disregarded the claim, saying more investigation was warranted.

U.S. President Barack Obama and U.K. Prime Minister David Cameron strongly supported the theory that a bomb caused the Russian plane to crash. British flights to the Egyptian resort Sharm el-Sheikh were suspended and efforts were made to evacuate some 20,000 Britons on vacation in the area.

Despite initially downplaying such theories, Russian President Vladimir Putin also decided to suspend flights to Egypt on recommendation of his security chief.

"Until we have determined the true reasons for what happened, I consider it expedient to stop flights by Russian aviation to Egypt," said FSB security service leader Alexander Bortnikov.

The government of Egypt has held strong in its dismissal of the terrorist claims, calling such suggestions "premature," "surprising" and "unwarranted."

The New York Times reports Egypt's investigations have been conducted secretly, leading some critics to believe the government is attempting to hide something.

"I don't anticipate the Egyptian investigation here to be any more transparent than their work on EgyptAir 990," said James E. Hall, former head of the National Transportation Safety Board.

Hall was involved in the investigation of crash of EgyptAir Flight 990 in 1999. Evidence pointed to the crash being caused by a suicidal pilot, but Egypt declared it was due to a plane malfunction.

"The air safety investigators in Egypt are under the thumb of the government," Hall said, "and I don't think that has changed."