Capitol officials are bracing for the 13th anniversary of 9/11, which has taken on more ominous significance due to the rise of the Islamic State in Iraq and Syria (ISIS).
Some Senate staff were told to keep their car keys and wallets on their person at all times this week in case the Capitol is evacuated. Staffers were not warned of any specific threat, however.
Senate staffers also said they expect a larger police presence on Capitol Hill this week.
One senior Democratic aide said U.S. Capitol Police have been “more meticulous” about checking IDs.
“In regard to the anniversary of 9/11, there will be multiple layers of security enhancements throughout the Capitol Complex; some measures will be visible and others will not,” said Officer Shennell Antrobus, a spokesman for the Capitol Police.
Antrobus said the force would maintain “a constant state of vigilance” and work closely with partners in law enforcement to share intelligence.
“Actionable intelligence information is important as it helps us modify our security plans, when necessary, and coordinate operations,” he said.
The police have taken a relatively low-profile approach to bolstering security to avoid raising anxiety.
A Senate chief of staff told The Hill Wednesday that he had not seen any email or alert from officials raising the threat level.
Lawmakers have become more concerned about the potential for a terrorist attack on U.S. soil since reading reports that American citizens have traveled to Syria to train with ISIS.
House Intelligence Committee Chairman Mike Rogers (R-Mich.) warned last month that hundreds of U.S. citizens have trained with the extremist Sunni militant group.
Rep. Pete King (R-N.Y.), the former chairman of the Homeland Security Committee, says ISIS now poses a greater domestic threat than al Qaeda did in the aftermath of 9/11.
There have been signs of increased security at other potential terrorist targets in Washington. A soldier carrying an assault rifle was spotted on what appeared to be a patrol near the Pentagon Metro station on Tuesday.
Federal officials seemed to be caught flat-footed when Islamic militants attacked the U.S. diplomatic compound in Benghazi, Libya, on the 11th anniversary of 9/11 in 2012.
President Obama met with his counterterrorism advisers Tuesday to go over security preparations for this year’s anniversary.
Lisa Monaco, the president's national security czar, has spent the past several months meeting with officials across the government to "review our security posture in light of not only this anniversary but the range of global threats we face," White House press secretary Josh Earnest said in a statement.
"The president’s national security team is continuing to take measures to prevent attacks against the homeland and ensure the protection of U.S. persons and facilities abroad — the administration’s top national security priorities," Earnest said.
— Justin Sink contributed.