(Official White House photo by Pete Souza)

President Obama has received briefings from FBI Director Robert Mueller and Department of Homeland Security Secretary Janet Napolitano on the situation in Boston, a White House official says, including the ongoing coordination with state and local officials.  

The security perimeter around the White House has been expanded "out of an abundance of caution," Secret Service spokesman Ed Donovan confirmed.

Massachusetts Gov. Deval Patrick said he has spoken to the president, who has directed his administration to provide whatever assistance is necessary in the investigation and response. The president also called Boston Mayor Tom Menino.