Boston Marathon Terror Investigation In Its 'Infancy,' FBI Says

Authorities investigating the bombings at the Boston Marathon warned on Tuesday not to expect immediate answers about who was behind the explosions that ripped apart the race's finish line Monday afternoon.

Even as the public poured in tips -- more than 2,000 by noon on Tuesday -- and the FBI vowed to "go to the ends of the Earth," in its search, authorities speaking at an evening press conference in Boston did not announce any major break in the case.

"The investigation is in its infancy," said Richard DesLauriers, the FBI's special agent in charge. "We are doing this methodically ... yet with a sense of urgency."

"The range of suspects and motives remains wide open," DesLauriers said.

CLICK HERE for live updates.

The search for forensic evidence turned up pieces of black nylon that could have been from a bag or backpack at both blast sites, DesLauriers said. Law enforcement sifting through the damage also recovered pieces of BBs and nails, possibly from a pressure-cooker explosive device used to maximize injuries.

No group or individual has claimed responsibility for the attack, which killed at least three people and wounded more than 180 others.

"Someone knows who did this," DesLauriers said. "The person who did this was someone's friend, neighbor or co-worker."

The podium for Tuesday evening's press conference at the Westin Hotel was filled with officials, including Massachusetts Gov. Deval Patrick; Boston Mayor Tom Menino, recovering from leg surgery and seated in a wheelchair; Police Commissioner Ed Davis; and others drawn from the vast ranks of the law enforcement agencies involved in the case.

Patrick urged observers and Boston residents to refrain from racial profiling as the investigation continues.

"There are times when all kinds of forces conspire to make people think of categories of people sometimes in uncharitable ways," he said, adding that no such incidents stemming from the attacks have been reported. "We are one community and we are all in this together."

A series of vigils are planned across the greater Boston area in the coming days, including an interfaith service scheduled for the Cathedral of the Holy Cross in the city's South End on Thursday morning.