Russian investigators on Monday sifted through the wreckage of an Aeroflot jet that crashed in the Ural mountains killing all 88 people on board, as the region marked a day of mourning.
The Boeing-737 plane plunged out of the sky on Sunday as it was coming in to land in the city of Perm, narrowly missing densely-populated residential areas. Witnesses said the plane was already on fire or exploded before the crash.
The Kommersant daily called the crash "one of this country's most mysterious air disasters," quoting the chief air traffic controller as saying that the pilot was behaving "abnormally" and was not following basic instructions.
The plane ascended instead of descending for landing on its second approach and turned left instead of bearing right. But when asked, the pilot told the controller, Irek Bikbov, that everything was fine, Kommersant reported.
"We are looking at various possible explanations for the accident. Currently the main one is that it was a technical fault," Vladimir Markin, an investigator from the Russian prosecutor's office, told Interfax news agency.