As the Winter Olympics approach, Sochi is even more on edge as Russian security officials search for a female suicide bomber believed to be in city limits.

Officials are hunting for three women altogether, possible suicide bombers that are known as "black widows" in reference to the belief that they are avenging dead husbands or other male relatives, The Associated Press reported.

Ruzanna Ibragimova, 22, is believed to be at large in Sochi, according to a police letter seen by an AP reporter. She is the widow of an Islamic militant.

"We know some of them got through the perimeter," Rep. Michael McCaul, chairman of the U.S. House Homeland Security Committee, told the AP. "She's for real. What we don't know is how many more black widows are out there."

Russia has been turbulent even as officials tighten security leading up to the Olympics. The city of Volgograd in the south was the scene of two suicide bombings last month. Thirty-four people were killed, and many more were injured, the AP reported.

McCaul and other Americans have been working with officials in Moscow and Sochi to improve security.

United States officials have information that could help keep people safe at the games if the Russians are willing to work with them, McCaul told the AP.

"The one improvement I would ask of the Russians is to allow our intelligence services to coordinate and cooperate better with theirs," he said.

Sochi security officials were not available for comment to the AP on Tuesday.

Besides the worrying fact that a black widow was able to get in after security tightened, McCaul wondered if militants could have infiltrated Sochi earlier.

"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."

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