WASHINGTON — Police are investigating letters that arrived today at Capitol Hill offices containing a photo of the Times Square military recruiting office before it was bombed and including the words “We did it.”

A law enforcement official, who spoke on condition of anonymity because the case is ongoing, confirmed the letter’s contents and said police are investigating.

A Capitol Police spokesman, Sergeant Kimberly Schneider, said she had received media calls asking about the letter. She said she had made some initial checks but had not been able to confirm reports of the letter.

The Associated Press obtained a copy of an e-mail from the office of Senator Feinstein, Democrat of California, to other lawmakers today that reads:

“A few offices on the House side have received a letter today addressed to ‘Members of Congress’ with a picture of a man standing in front of the Times Square recruiting station that was bombed in New York today with the statement ‘We did it.’ He is standing in front of it with his arms spread out and he’s attached his political manifesto.”

The e-mail says the recipients were told to leave the letters alone and call police.

The small bomb caused minor damage to the New York military recruiting station before dawn today, and police were searching for a hooded bicyclist seen on a surveillance video pedaling away.

The blast left a gaping hole in the front window and shattered a glass door, twisting and blackening its metal frame. No one was hurt, but police Commissioner Raymond Kelly said the device, though unsophisticated, could have caused “injury and even death.”