Just to be safe, the NYPD has increased security around the city in response to the twin explosions at the Boston Marathon. "We're stepping up security at hotels and other prominent locations in the city through deployment of the NYPD's critical response vehicles (CRVs) until more about the explosion is learned," deputy police commissioner Paul Browne says in a statement.
In D.C., meanwhile, Pennsylvania Avenue outside of the White House has been closed, according to Zeke Miller. President Obama has been notified of the attack, obviously, and has "directed his administration to provide whatever assistance is necessary in the investigation and response."
Update, 5:30 p.m.: Mayor Bloomberg has released the following statement:
"As law enforcement authorities investigate today's explosions in Boston, I ask all New Yorkers to keep the victims and their families in your thoughts and prayers. I have spoken with Police Commissioner Ray Kelly, and the NYPD has stepped up security at strategic locations and critical infrastructure, including our subways. Some of the security steps we are taking may be noticeable, including deployment of Critical Response Vehicles and additional police personnel, and others will not be. We have 1,000 members of the NYPD assigned to counter-terrorism duties, and they - along with the entire NYPD and the investments we have made in counter-terrorism infrastructure - are being fully mobilized to protect our city."