The first 10 bodies of victims of Saturday's plane crash over Egypt were identified by their families Tuesday, Russian officials said.

Metrojet's Airbus A321-200 en route from Egypt's Sharm el-Sheikh to St. Petersburg crashed over the Sinai Peninsula on Tuesday, killing all 224 on board. The overwhelming majority of the passengers were Russian holidaymakers flying home.

Alexei Smirnov of the Russian emergency situations ministry said that a total of 140 bodies and more than 100 body parts were delivered to St. Petersburg on two government planes on Monday and Tuesday and that a third plane is expected to bring more remains later on Tuesday.

Confusing reports and theories emerged on Monday as to what could have caused the crash.

Some aviation experts raised the possibility that a bomb on board the Airbus brought it down, while others cited an incident in 2001 when the aircraft grazed the runway with its tail while landing.

Metrojet firmly denied that the crash could have been caused by either equipment failure or crew error.

In Egypt, the U.S. Embassy has instructed its staff not to travel anywhere in the Sinai Peninsula pending the outcome of the investigation into the crash as a "precautionary measure."

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Nataliya Vasilyeva contributed to this report from Moscow.