A 28-year-old female schoolteacher from the North Caucasus may have been the second suicide bomber who attacked the Moscow Metro, a Russian newspaper says.
The woman's father, Rasul Magomedov, told Novaya Gazeta that he recognised his daughter Mariam Sharipova in a photograph circulated on the internet.
"The last time my wife saw our daughter she was wearing the same red scarf as in the photograph," he said.
The blasts last week killed 40 people. The other bomber has been identified.
A Chechen militant leader, Doku Umarov, has said he ordered the 29 March rush-hour bombings, which also injured more than 80 people, most of whom are still in hospital.
Mr Magomedov said he and his wife "cannot imagine how Mariam turned up in Moscow".
His daughter had been teaching computer science since 2006 at a school in the village of Balakhani in Dagestan, he said. She lived with her parents, both of whom are teachers in Balakhani.
Mr Magomedov told the Russian daily Kommersant that he had gone to the police on 3 April and they had taken a sample of his DNA.Last week the Russian authorities identified one of the suicide bombers as a 17-year-old girl from Dagestan - Dzhennet Abdurakhmanova. She was believed to be the widow of a senior Caucasus militant killed by Russian security forces in December.
Dagestan, like nearby Chechnya, is struggling to quell militant violence.
Mr Magomedov said Mariam had gone shopping with her mother in the Dagestani capital Makhachkala on Sunday 28 March - the day before the Moscow attacks.
That Sunday afternoon she rang her mother to say she would be visiting a friend and would return home by herself. That was the last they saw of her, Mr Magomedov said.
"She worshipped, but she never expressed any radical beliefs," he said.
Novaya Gazeta says that if confirmed, the story casts doubt on the Russian official theory that both female suicide bombers travelled to Moscow by bus from Kizlyar, a Dagestani town near the Chechen border.
The Kizlyar-Moscow bus journey takes 36 hours, the paper reports - yet Mariam Sharipova was still in Makhachkala on the Sunday afternoon.
The attacks came almost a year after Russian President Dmitry Medvedev declared an end to Russia's "counter-terrorism operations" in Chechnya, in a bid to "further normalise the situation" after 15 years of conflict that claimed more than 100,000 lives and left it in ruins.
Despite this, the mainly Muslim republic continues to be plagued by violence, and over the past two years Islamist militants have stepped up attacks in neighbouring Ingushetia and Dagestan.