Arlington National Cemetery announced on Friday that it is heightening security and implementing new identification checks “due to current conditions.” All visitors 16 and older are now required to present a photo ID at the entrance until further notice.

The cemetery’s statement doesn’t specify the “current conditions” that prompted the policy change, but the policy was announced immediately after the drone strike ordered by President Donald Trump killed Iranian Gen. Qassem Soleimani at Baghdad’s airport early Friday morning. Iranian President Hassan Rouhani and its Supreme Leader Ayatollah Ali Khamenei have both promised retaliation.

In the hours that followed, cities across the country announced that they were on high alert for suspicious activity. D.C. Mayor Muriel Bowser said in a statement that while there were no immediate threats to the city, “we remain vigilant and [Metropolitan Police Department] & [Homeland Security and Emergency Management Agency] will remain in close contact with regional and federal partners to monitor evolving events—both at home and abroad.”

The National Park Service also told the Associated Press that it would step up patrols at major federal sites and monuments in the District. And Bethesda’s Navy Base, home to Walter Reed National Military Medical Center, is changing the schedule on gates to access the facility.

At Arlington National Cemetery—which is operated by the Department of the Army—all visitors 16 and older are now required to issue a state- or government-issued ID at the entrance. Visitors who are 16 or 17 years old will be able to submit a school ID, and foreign nationals can use a passport.

Previously, photo identification was only required for visitors coming by car (those attending funerals or who have permanent passes to visit a grave site, or employees). The cemetery tightened security protocols in 2017, limiting the number of entry points and requiring physical security screening.

It’s not clear how long the new photo identification policy will be in place. A spokesperson for the cemetery declined to comment on the record and the media affairs office has not returned an emailed request.