Authorities today were investigating whether an explosion at the Times Square military recruiting office was connected to strikingly similar bombings at two foreign consulates in New York, but ruled out a link to mysterious letters sent to Capitol Hill offices.

Investigators were also scrutinizing surveillance video and forensic evidence after a bicycle-riding bomber struck the landmark station yesterday, scarring one of the world’s most recognizable locations.

Authorities said there was no connection between the blast and a letter sent to as many as 100 members of Congress bearing the words “Happy New Year, We Did It.”

The lengthy anti-war letters — which arrived with photos of a man standing in front of the recruiting office before it was damaged — contained no threats, officials said.

An FBI spokeswoman in Los Angeles, Laura Eimiller, said an individual was questioned there about the letters to Congress and “there is no evidence linking the letters, which contained no threat, to the bombing.”

A law enforcement official in Washington, who spoke on condition of anonymity because the investigation of the bombing is continuing, called the timing of the letters an “incredibly unbelievable coincidence” and said no charges were expected in connection with them.

Democratic lawmakers were startled to receive the letters in their office mail just hours after the early morning New York bombing, and turned them over to the Capitol Police.

One law enforcer said the “We did it” referred to the Democratic wins. The Democrats gained control of Congress in 2006.

The Times Square bomb, contained in a metal ammunition box, produced a sudden flash and billowing cloud of white smoke. When the smoke cleared, there was no serious damage, nor any clear indication of a motive.