An engine fire — not a terror attack — appears to have caused the crash of a Russian jet that killed all 88 people on board, officials said Monday.

The right engine of the Boeing 737-500 apparently failed and caught fire as the plane was preparing to land Sunday in the city of Perm in the Ural Mountains, said the chief of Russia's federal Investigative Committee, Alexander Bastrykin, who is in charge of the crash probe.

Russia's Transport Minister Igor Levitin said that no trace of explosives had been found on the crash site about 750 miles east of Moscow. Levitin refuted earlier reports that claimed the plane had exploded in the air and media allegations that it could have been brought down by a terror attack.

The plane slammed into the ground on the outskirts of this industrial city of 1 million people just a few hundred yards from small wooden houses and apartment buildings. Officials said no one on the ground was killed.

Flight 821, operated by a subsidiary of national flag carrier Aeroflot, carried 82 passengers, including six children under 10, and six crew members, Aeroflot said.

Aeroflot officials said the plane was circling at about 3,600 feet in "difficult weather conditions" — including low cloud cover and rain — when it suddenly crashed.

Flight controller Irek Bikbov told Channel One television that the plane's pilot was behaving in a strange way, disobeying orders to go lower on the final approach and instead taking the jet to a higher altitude.

When he asked the pilot whether things were normal on board, the pilot answered positively but his voice was strained as if under stress, Bikbov said.

"He was behaving in a strange manner and wasn't following my orders," Bikbov said.

The plane's flight recorders have been found, and officials said it will take three to four weeks to analyze them.

The jet crashed on a railroad embankment, damaging a section of the track. Parts of the plane's fuselage reading "Aeroflot" and "Boeing" lay askew on the rails, along with clothing, life preservers and engine parts. The crash briefly disrupted traffic on a section of the Trans-Siberian railway.

Emergency workers in camouflage uniforms picked up human remains and placed them in blue bags. Relatives of passengers were asked to provide blood and DNA samples to help in the identification, which is expected to take weeks.

Pavel Shevchenko, a 36-year-old Perm resident who lives just 300 yards from the crash site, said he was awoken by an explosion and ran outside. Shevchenko said he feared his acquaintances or friends could be among the dead.

"It's awful. There's just no words to describe it," he told The Associated Press.

Russia and other former Soviet republics have some of the world's worst air traffic safety records in recent years, according to the International Air Transport Association. Experts blame weak government regulation, poor pilot training and a cost-cutting mentality among many carriers.

No problems were reported with the 15-year-old jet when it was last inspected at the beginning of 2008, Aeroflot deputy director Lev Koshlyakov said. The plane had been used by a Chinese carrier before the Aeroflot subsidiary, Aeroflot-Nord, leased it earlier this year.

Among those killed was Gennady Troshev, 61, a retired army general who commanded troops in Chechnya. Human rights activists had accused him of tolerating rampant abuses in the war-ravaged republic.

Sunday's crash was the second involving a Boeing 737 in the former Soviet Union in the past month. A Boeing flying from the Central Asian nation of Kyrgyzstan to Iran crashed shortly after takeoff Aug. 24, killing 64 of the 90 people on board.

The pilot of that plane has been detained by prosecutors, officials said this week.