SOCHI, Russia — Security officials are hunting down three potential female suicide bombers, one of whom is believed to be in Sochi, where the Winter Olympics will begin next month.
Police leaflets at a central Sochi hotel on Tuesday contained warnings about the three suspects. A police letter said that one of them, Ruzanna Ibragimova, a 22-year-old widow of an Islamic militant, was at large in the city.
A US congressman who was in Sochi on Tuesday to assess the situation said he was impressed by the work of Russian security forces but troubled that potential suicide bombers had gotten into the city, despite all of the extraordinary security measures.
‘‘We know some of them got through the perimeter,’’ said Representative Michael McCaul, Republican of Texas and chairman of the House Homeland Security Committee. ‘‘She’s for real. What we don’t know is how many more black widows are out there.’’
Russian authorities have blamed the widows of slain insurgents for previous suicide attacks in the country.
The Black Sea resort city will host the Games amid concerns about security and potential terrorist attacks.
The southern city of Volgograd was rocked by two suicide bombings in late December that killed 34 and injured scores. An Islamic militant group in Dagestan posted a video on Sunday claiming responsibility for the bombings and threatened to strike the Games in Sochi, about 300 miles west of Dagestan.
McCaul said he had numerous meetings with officials in Moscow and Sochi and was briefed by the joint operation center in Sochi, which is responsible for overall security in the area.
‘‘The one improvement I would ask of the Russians is to allow our intelligence services to coordinate and cooperate better with theirs,’’ McCaul said. Although the Russian side was confident that it could provide security, the United States has information that could help keep the Games safe, he said.
The New York Times reported that the United States and Russia have opened discussions about using sophisticated US electronic equipment, developed by the Pentagon to counter improvised explosive devices in Afghanistan and Iraq, in a new effort to help secure the Winter Olympics.
The potential for a technological exchange was part of an extensive discussion in Brussels on Tuesday when General Martin E. Dempsey, the chairman of the Joint Chiefs of Staff, held his first face-to-face meeting with his Russian counterpart, General Valery Gerasimov, chief of the general staff.
The Defense Department would be willing to provide equipment designed to detect and disrupt cellphone or radio signals used by militants to detonate improvised explosives from a distance, Dempsey said. But he cautioned that technical experts from both nations first needed to make sure that the US systems could be integrated into the communications networks and security systems being set in place by Russia.
In discussing the Pentagon’s technology to counter improvised explosives, Dempsey noted that this was “something that we’ve become extraordinarily familiar with.” Homemade bombs planted by militants have been the leading cause of deaths and injuries to US service members in Afghanistan and Iraq.
But especially during the early implementation of the technology, the US military found it had created a muddle of electronic signals in which competing and overlapping systems canceled out the effectiveness of other systems in use at the same time and in the same area.
“If you’re not careful, you can actually degrade capability, not enhance it,” Dempsey said.
The discussion between Dempsey and Gerasimov came one day after Pentagon officials disclosed that the US European Command was drawing up plans to have two Navy warships in the Black Sea at the time of the Sochi Games, should they be needed in case of emergency. The Games begin Feb. 7.
During their meetings here, the US and Russian military chiefs sought to advance an agenda of exchanges and continued cooperation on counterterrorism and anti-piracy operations even as diplomatic relations between Washington and Moscow swing between caustic disagreement and cautious cooperation.
Dempsey, in an interview with the Times, said it was important for the two militaries “not to foreclose on conversations, even if at some points there are disagreements that prevent the forward movement” in other parts of the relationship, whether political or diplomatic.
McCaul expressed concern that terrorists could have gotten into Sochi before security was tightened.
‘‘How many potential cells could be in Sochi and the Olympic village?’’ he said. ‘‘But after ‘the ring of steel’ was implemented we have this one person who seems to have been able to penetrate it. It does demonstrate vulnerability.’’
Police material distributed to the hotel staff included pictures of two other women in veils: 26-year-old Zaira Aliyeva and 34-year-old Dzhannet Tsakhayeva. It said they had been trained ‘‘to perpetrate acts of terrorism.’’
It warned that the two women ‘‘are probably among us,’’ but, unlike Ibragimova’s case, did not say whether they are in Sochi.
Russian troops also have been active fighting militants in Dagestan, one of the predominantly Muslim republics in Russia’s North Caucasus and the center of an Islamic insurgency that has engulfed the region.