Moscow, Russia - Bomb investigators believe a member of an Islamist group in southern Russia may be behind the Moscow airport attack in which 35 people died, reports say.
Reports say Vitaly Razdobudko, from Stavropol on the edge of the northern Caucasus, either organised or carried out the attack.
The ethnic Russian is being linked to a 31 December explosion at a house in the centre of Moscow in which a woman died.
The authorities have made no official comment on their inquiry.
It is still not clear if a man or a woman was involved in Monday's attack in which a bomber detonated up to 7kg (15lb) of TNT at Domodedovo airport.
But Russian media say the suspect is being linked to Islamist group Nogai Jamaat (Nogai Battalion).
The woman who died in Moscow on New Year's Eve was found with the remains of a suicide belt, according to reports, and she was said to have been married to a militant from the group who was arrested last year.
No group has claimed to have organised the airport attack, the BBC's Steve Rosenberg reports from Moscow.
Prime Minister Vladimir Putin has said he does not believe the bombing was linked to Chechnya but Chechnya is just one of a number of conflict-ridden republics in the Russian North Caucasus, our correspondent notes.
Nogai Jamaat is active in parts of Dagestan and Russia's Stavropol region and has carried out a number of terror attacks across the North Caucasus.
Meanwhile, security at Russian airports continues to be a concern, our correspondent adds.
The front page of one Russian newspaper on Thursday carries a photograph of a fake bomb.
A journalist is said to have smuggled it into Domodedovo airport on Wednesday without it being detected.