U.S. Transit Systems on Code Orange

Gary McLhinney, chief of the Maryland Transportation Authority Police, who patrols BWI Airport, the MARC commuter trains and the tunnels on Interstate 95, said bomb-sniffing dogs and officers armed with assault rifles were sweeping trains and the airport. Other officers were riding trains and monitoring commuters on platforms, he said.

Police chief Ramsey said Washington commuters will see more D.C. police officers at Metro stations and some of those officers will be armed with machine guns. Extra bomb technicians are also on duty and other specialized units have been activated, Ramsey said.

Ramsey said police officers were held over from the last shift to increase manpower in Washington today. He said a joint operations command has been set up and officers from surrounding jurisdictions have also been called in to help.

At the U.S. Capitol, police announced that they had begun inspections of all large vehicles, such as buses and tour mobiles, and would continue the inspections during morning and afternoon rush hours.

In New York, police "redirected forces to the transit system, put greater attention to other sensitive locations, and thousands of additional police are working," police spokeswoman Dora Kalbouros said.

Amtrak also increased security. Officials with the passenger railroad said they had increased police staffing on board all trains, at stations and along rail lines. They have also brought in canine units.

Heightened security was to continue until investigators have a better understanding of what happened in London, Amtrak said.

If Washington riders detect anything out of the ordinary on Metro, they should call 202-962-2121. To report any other suspicious activity in D.C., call 202-727-9099.

Washington Post Staff Writers Steven Ginsberg, Theola S. Labbe, David Snyder, Marc Fisher, Spencer Hsu, Mary Beth Sheridan, Sara Kehaulani Goo, Michael Alison Chandler, Eric M. Weiss and Yolanda Woodlee contributed to this report.