Thirty-one people were confirmed killed and 12 others injured in a passenger plane crash in Russia's Siberian region early Monday, Russian emergency authorities said.

The injured remained in critical conditions, according to the authorities.

Russian President Dmitry Medvedev expressed his condolences to the families of victims and called on local officials to spare no efforts in treating and saving lives of the injured.

Russian Health and Social Development Minister Tatiana Golikova said the 12 people injured, who suffered from broken bones and severe burns, were rushed from the site of the plane crash to nearby clinics. Five of them have undergone surgeries.

Due to the crash, Medvedev put off a planned meeting with leaders of unregistered political parties.

Following the tragedy, the Tyumen region announced an observance of three-day mourning starting Wednesday, during which flags will be flown at half-mast and all entertainment events will be canceled, according to the regional authorities.

The aircraft, a French-Italian-made ATR-72 mode and owned by UTair Airlines, with 39 passengers and four crew members aboard, was destined for a flight between Tyumen and Surgut, both in Siberia. It went down at around 5:50 a.m. Moscow time (0150 GMT) shortly after it took off from the airport in Tyumen, a key Siberian city about 2,100 kilometers east of Moscow.

Rescuers rushed to the site of the plane crash, where the snow was knee-deep, after the accident and transported the injured to nearby hospitals. Some of the critically injured were pronounced dead later. All passengers and crew members have been found.

According to a list of passengers and crew published by UTair Airlines, most of those people aboard the ill-fated plane were from the two Russian cities of Tyumen and Surgut. There were no foreign nationals on the crashed plane.

Yuri Alekhin, head of the regional branch of Russia's Emergency Situations Ministry, told reporters that the French-Italian-made ATR-72 aircraft disappeared from the radar and lost contact just three minutes after taking off. He said they had found the crashed aircraft's two black boxes, which were in good condition.

A UTair Airlines source also confirmed the plane failed in an attempt to make an emergency landing before bursting into flame. The fire was later extinguished. It denied fatigue of crew was the cause of the tragedy.

Witnesses said that they noticed smoke coming from the aircraft 's twin engines when it plunged to the ground.

The possibility of a terrorist attack for the plane crash has been ruled out. The Russian Investigation Committee contended that a technical failure might be the most likely cause of the tragedy.

On-site search and rescue operation finished at midday and an investigation into the cause behind the crash was under way.

A team of the Interstate Aviation Committee arrived at the scene to conduct a technical inquiry, with participation of French, Canadian and British experts.

Special telephone lines have also been opened to offer information about the air crash and psychological counseling.

ATR-72 aircraft is a twin-engine, turboprop medium-haul passenger airliner, which is designed for the transportation of 74 passengers and is steered by two pilots.