Russia flew thousands of tourists home from Egypt's Red Sea resort of Sharm el-Sheikh on Saturday and Sunday, as the first of three Russian inspection teams headed to the region to examine airport security.

At the same time, an insider with the Egyptian investigation into what caused the downing of a Russian Metrojet flight last week, which killed all 224 people on board, told Reuters news agency that they could say with "90 percent" certainty that a bomb had caused the tragedy.

"The indications and analysis so far of the sound on the black box indicate it was a bomb," said the investigator, who asked to remain anonymous. "We are 90 percent sure it was a bomb."

Lead investigator Ayman al-Muqaddam told a press conference on Saturday that the aircraft had broken up in midair while it was on autopilot, and that a noise could be heard in the last second of the cockpit black box recording. He declined, however, to draw any firm conclusions about why the plane crashed.

'IS' has 'eclipsed al Qaeda'

The Reuters report confirms suspicions voiced by the US and UK that the disaster was the result of a terrorist attack. Representative Adam Schiff, a top Democrat on the US House Intelligence Committee, said in a television interview on Sunday that if it was indeed a bombing carried out by "Islamic State" (IS) affiliates, then it would have "fully eclipsed al Qaeda as the gravest terrorist threat in the world."

According to information circulating from the intelligence community, known IS affiliates in Egypt's restive Sinai peninsula have already been recorded boasting about the attack, and had received a commendation from the terrorist group's leadership in Raqqa, Syria.

The United Kingdom and several airlines have stopped flights to the resort, while Russia has suspended air travel out of Egypt completely. According to The Associated Press, security officials at Sharm el-Sheikh airport have long complained of lax security practices - such as malfunctioning baggage screening devices, cursory searches at the entry gate for airplane food and fuel, and poorly paid, easily bribed policeman conducting the carry-on X-rays.

es/bk (AP, AFP, Reuters)