Moscow, Russia (CNN) -- Russian investigators on Friday identified one of the female suicide bombers in the Moscow metro attacks that killed dozens of people as teenager Dzhennet Abdullayeva.
The committee's press office told CNN that Abdullayeva was the suicide bomber at the Park Kultury metro station on Monday. She was born in 1992, the office said, but could give no further details as to her age.
The investigators established her identity "after a series of forensic and genetic examinations as well as identification procedures," the committee said.
It said the identity of the second female bomber is under investigation.
A number of Russian newspapers reported Friday that Abdullayeva -- whose last name has also been cited as Abdurakhmanova -- was the widow of a prominent Dagestani rebel militant leader who was killed by federal forces in late December.
Monday's blasts tore through the Lubyanka and Park Kultury stations in central Moscow -- the female bombers detonating their explosives about 40 minutes apart, beginning just before 8 a.m. (midnight ET).
An estimated 500,000 people were riding trains in the capital at the time of the attacks.
The death toll, which had stood at 39, apparently rose to 40 when a 51-year old man died Friday morning in a Moscow hospital, according to Russian state television.
A photograph of Abdullayeva and her late husband, identified as 30-year-old Umalat Magomedov, was distributed by Newsteam, and published in Russian media, including the Kommersant newspaper.
The photograph shows a bearded man with his arm draped over a young-looking teenage girl dressed in traditional Muslim attire. Both are holding guns and looking unsmilingly into the camera. It is not immediately clear why the two do not share the same last name.
The circumstances of the photograph, including when it was taken, were not explained. CNN could not confirm the authenticity of the picture.
The Russian Investigative Committee said Abdullayeva was from Dagestan, a predominantly Muslim republic in southern Russia that has faced separatist violence for years. On Wednesday, two bombs exploded there, killing a dozen people, most of them police officers. Later in the day, a car -- possibly carrying a homemade explosive device -- exploded, killing two men and wounding one more, Russian state-run news agency Itar-Tass reported.
On Friday, Russia's Federal Security Service and police identified "organizers and some of the executors" of the Moscow bombings and city of Kizlyar, according to a written statement from authorities released to Russian news agencies. No further details were given.
Russian Prime Minister Vladimir Putin had said earlier this week that he doesn't rule out the double bombings in Dagestan were carried out by the same terrorist groups behind Monday's attacks.
The next day, President Dmitry Medvedev arrived in Dagestan, where he held a meeting about the situation with the heads of republics in the North Caucasus, territorial units of Russia's Federal Security Service, and the Interior Ministry.
Ahead of the president's visit, Chechen rebel leader Dokku Umarov claimed that he gave orders to attack the Moscow subway, according to a Chechen rebel Web site.
Kavkaz Center, a Web site that regularly carries messages from the rebels, released a video in which Umarov said he was behind Monday's attacks.
On Friday, Medvedev spoke in his Kremlin office with leaders of the Russian parliament, saying in remarks carried on Russian television that the ban on the death penalty in Russia was not his choice. He said that some of the lawmakers have raised the possibility of reinstating the death penalty.
"If I worked here in the 1990s, the decisions would have been different -- but it's useless to discuss this now," he said.
Russia imposed a moratorium on the death penalty a little more than a decade ago, although the country's courts stopped handing down death sentences a few years earlier than that, after Russia was accepted into the Council of Europe. The last death sentence was carried out in September 1996.
"Nevertheless, those who committed those appalling crimes, will pay for that -- with their own lives, regardless of the ban on the death penalty," he said. He would not elaborate.
The Russian president also said that it was "short-sighted to say that terrorism stems only from social problems."
He said, "Yes, we should set the Northern Caucasus in order and provide those living there with a normal life. But not just that. It is useless to reform some people..."