U.S. transit agencies beefed up security as a precaution Monday following the suicide bombing in Moscow's subway system, sending more police into stations and having officers conduct random inspections of rail yards.
In New York, caravans of police vehicles were dispatched to transit hubs, and officers assigned to subways overnight were held in place so they overlapped with the day tour. Special units distinguished by their special black uniforms, helmets and body armor also were assigned to transit facilities.
In Washington, D.C., Metro police were conducting random inspections of stations and rail yards, officials said. Atlanta's public transit system said its police department was increasing the number of officers and patrols throughout the system.
The Transportation Security Administration said in a statement late Monday that it is working closely with transit security agencies and local law enforcement.
The TSA and the Department of Homeland Security they have no specific or credible information indicating a current threat to U.S. transit systems, the statement said, but security is being stepped up as a precaution. The statement asked passengers to be vigilant and to expect additional security measures.
Russian authorities saidin Moscow on Monday in a subway jam-packed with rush-hour passengers, killing dozens. They blamed the carnage on rebels from the Caucasus region.
"This is very much a Russian issue but the problem is that these terrorist attacks these days are viral. And working through the Internet, they spread a message. And the concern in any capital around the world, any major cosmopolitan area with a subway system, is that you've got to worry about your own people too," Marvin Kalb, a professor at Shorenstein Center for Press and Public Policy at Harvard's Kennedy School of Government, told CBS Radio News.
Transit continues to be one of the most vulnerable sectors in the U.S., reports CBS News correspondent Bob Orr. Unlike airplanes, trains are not heavily guarded or widely protected against explosives. Terrorists fully understand the weakness and have exploited it a number of times. Attacks in Madrid and London show that Islamist extremists have rail systems on their hit list.
And while there has never been an attack against a U.S. rail system, Najibullah Zazi was in the final stages of plotting to bomb New York subways when he was arrested by the FBI last fall. Heto planning the attack last month.
"This isn't isolated to Moscow or to London or to Madrid. This is a problem the United States has to worry about and no doubt is a continuous headache for counterterrorism and homeland security officials," CBS News national security consultant Juan Zarate told CBS Radio News.
Caucasus Islamic separatists tend to be focused on targets in the region, primarily Russia, and are not generally considered a threat to U.S. domestic interests.
In Chicago, the city police department's public transportation section and Chicago Transit Authority personnel were watching closely for any suspicious activity or behavior, said CTA spokeswoman Kim Myles. Representatives of transit agencies in Boston and Philadelphia said they believed their normal security practices were vigilant enough to protect the riding public.
The New York Police Department issued a statement saying it was increasing coverage of the city's subway system as a precaution "in response to the Moscow bombings."
The city's Metropolitan Transportation Authority acknowledged heightened security, but declined to provide details. The agency is in charge of New York City buses and subways, as well as suburban trains, and bridges and tunnels.
New York City "did ramp up our coverage a little bit this morning" after officials learned of the Moscow bombing, said Mayor Michael Bloomberg.
"We change it every day, and for security reasons obviously we're not going to tell anybody what we're doing," Bloomberg said. "But you can rest assured we have great interest in what goes on around the world."
New Yorkers told CBS station WCBS-TV that the added measures brought a welcome sense of security.
"It provides some sense of comfort to look up and see them but unfortunately the terrorists can still do what they want to do," said Alison Kline.
But for many others in Manhattan, where the public has grown accustomed to increased security after the 2001 terror attacks, the added measures are hardly noticed.
"I don't think it poses a threat here now," said Carlos Rivera, 44, of Newark, N.J., who commutes to New York City daily and works in sales.
"Every day, I see the NYPD out here. I see the dogs. I can't let it affect my life right now," said Rivera. "I don't think about terrorism. I only think about it when I hear about it. Other than that, it never enters my mind."
Andrew Davis, 24, who was catching a train home to Morristown, N.J., said he feels safe and didn't notice any increased security.
John Villegas, who said he used to work near the World Trade Center, remained sensitive to the heightened security.
"I'm a little wary," Villegas, 48, said at Pennsylvania Station as he waited for a train home to Woodbridge, N.J. "I do not feel safe right now. It's a little scary."