Story highlights Boeing sending technical team to assist in investigation

Russian media airs video that shows plane in vertical dive as it crashes

Flight recorders have been found, could provide data Tuesday, news agency says

The jet had 44 passengers and a crew of six aboard

The president of the Russian republic of Tatarstan declared Monday a day of mourning as crews continued to look for bodies in the wreckage of a Russian jetliner that crashed on landing a day earlier.

All 50 people on board, including the son of Tatarstan regional President Rustam Minnikhanov, died in the crash in Tatarstan's capital, Kazan.

Closed-circuit video, aired on Russian media outlets, shows the plane vertical to the ground as it crashes in the darkness, creating a large fireball and a wide fire on the ground.

The victims ranged in age from 13 to 87, according to a list of names the airline posted on its website . Among them was Lt. Gen. Alexander Antonov, the regional chief of Russia's Federal Security Service, and a British national.

"Not all the bodies have been located," Deputy Emergency Situation Situations Minister Vladimir Stepanov told local media Monday morning. "The main work will be completed today."

Officials do not know why Tatarstan Airlines flight 363 crashed. Authorities say they have confiscated documents and fuel samples from Tatarstan Airlines.

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Location of plane crash

Part of the answer may lie in the Boeing 737's flight and data recorders. Russian officials say they've found the flight recorders, the state-run RIA Novosti news agency said Monday.

Russia's Interstate Commerce Committee reports that the recorders' container was seriously damaged, the news agency said, but they've been sent to Moscow and could provide some information by Tuesday.

Boeing is sending a team to assist with technical aspects of the investigation, the company said in a written statement that also offered its condolences to the families of the victims.

The plane, carrying 44 passengers and a crew of six, took off from Moscow's Domodedovo International Airport, about 700 kilometers (435 miles) west of Kazan.

The pilot tried to land once before the plane crashed on the second attempt, officials said.

The jet was 23 years old and had been in service with at least eight airlines, including Air France, Uganda Airlines and Bulgaria Air, according to aviation industry websites.

In a November 2012 flight, it was forced to cut short a flight to Moscow and return to Kazan after losing cabin pressure, according to the website AeroInside.

Russia has tried to improve its checkered reputation for air safety in recent years.

In 2011, then-President Dmitry Medvedev grounded two classes of Soviet-era aircraft after a pair of crashes that killed more than 90 people, including a charter plane crash that killed an entire professional hockey team.

Medvedev said Russia would have to upgrade its aircraft fleet, step up safety standards and radically cut the number of airlines.