Photo of police officer participating in terrorism drill by erin_m.

UPDATE: (10:50 p.m.): Mayor Gray held a press conference around 10:30 p.m. this evening, stating that he had been briefed on “credible but unconfirmed threats” by Department of Homeland Security head Janet Napolitano.

Gray said that a 9/11 plan was already activated by the District’s public safety team, and that the city had been in a “heightened state” of vigilance since September 1. MPD Chief Cathy Lanier said that the District’s police force had begun preparations for the weekend eight months ago, and are “stepping up security in ways both visible and unseen.” (Meanwhile, police in Arlington say that they are aware of the threat, but are not taking any specific action as of yet.)

The District is not planning on canceling any weekend events at this point; Metro officials have also been briefed on the situation, and service is not expected to experience interruptions.

In short: if you see anything suspicious over the next few days, you should contact 311 or 911, if a crime is in progress.

With the tenth anniversary of the September 11 attacks approaching, federal officials have uncovered what they are calling a “credible but unconfirmed terror threat” against both Washington and New York City. The threat could potentially involve car or truck bombs.

The official statement on the threat, from Matthew Chandler, spokesman for the Department of Homeland Security:

It’s accurate that there is specific, credible but unconfirmed threat information. As we always do before important dates like the anniversary of 9/11, we will undoubtedly get more reporting in the coming days. Sometimes this reporting is credible and warrants intense focus, other times it lacks credibility and is highly unlikely to be reflective of real plots under way.

Regardless, we take all threat reporting seriously, and we have taken, and will continue to take, all steps necessary to mitigate any threats that arise. We continue to ask the American people to remain vigilant as we head into the weekend.

Chandler added that “intelligence gathered from the [bin Laden] raid” indicated that “Al Qaeda has shown an interest in important dates and anniversaries, such as 9/11.” Earlier this evening, NBC’s Pete Williams reported that the Metropolitan Police Department was informing police officers that they might be working longer shifts this weekend.

Unlike New York Mayor Michael Bloomberg, Mayor Vince Gray has not yet scheduled any kind of press briefing regarding the threat, though he is scheduled to attend a 9/11 remembrance tomorrow morning at 9 a.m.