UPDATE: 3:33 p.m.
Even thousands of miles from the Boston, distance runners are sharing their sympathy with victims of Monday's bombings.
The sport is supported by a tight-knit community, and Tuesday was a day to pay tribute to those harmed in the blasts at the end of the marathon.
On Twitter the runforboston hashtag became popular -- a simple motivation to get out, even for just a few miles. Organized through social media and local clubs, runners all over the country were wearing race T-shirts and planning vigils to honor Boston runners.
Some Boston College students used Facebook to plan a walk of the marathon's last five miles for Friday afternoon.
In Nebraska, the co-owner of a running equipment store based in Omaha turned a previously organized informal run into a Boston memorial.
UPDATE 12:43 p.m.
BOSTON (AP) -- A 29-year-old restaurant manager has been identified as one of three people killed in the bombing at the Boston Marathon.
Her father says Krystle Campbell, of Medford, Mass., had gone with her best friend to take a picture of the friend's boyfriend crossing the finish line on Monday afternoon.
William Campbell says his daughter, who worked at a restaurant in nearby Arlington, was "very caring, very loving person, and was daddy's little girl." He says the loss has devastated the family.
He says the friend was seriously injured in the explosion.
An 8-year-old, Martin Richard of Boston, also died. He was at the finish line watching the race with his family.
UPDATE 12:08 p.m.
WASHINGTON (AP) -- A person briefed on the Boston Marathon investigation says the explosives were in 6-liter pressure cookers and placed in black duffel bags.
The person says the explosives were placed on the ground and contained shards of metal, nails and ball bearings. The person spoke on the condition of anonymity because the investigation was ongoing.
The person says law enforcement officials have some of the bomb components but did not yet know what was used to set off the explosives.
President Barack Obama said Tuesday the bombings were an act of terrorism but investigators do not know if they were carried out by an international or domestic organization, or perhaps by a "malevolent individual."
UPDATE 9:50 a.m.
WASHINGTON (AP) -- President Barack Obama says the explosions at the Boston Marathon are being investigated as an act of terror, although authorities still don't know who is responsible.
He called the bombing "a heinous and cowardly act" used to target innocent civilians.
Obama spoke to reporters at the White House after a briefing by his national security team.
Three people were killed, including an 8-year-old boy, and more than 170 were wounded in Monday's bombing at the famous marathon's finish line.
Obama has ordered flags at the White House and all government buildings to be flown at half-staff.
Obama signed a proclamation making the order Tuesday morning, calling it a "mark of respect for the victims of the senseless acts of violence."
BOSTON (AP) -- Massachusetts Gov. Deval Patrick says no unexploded bombs were found at the Boston Marathon. He says the only explosives were the ones that went off Monday.
Three people were killed, including an 8-year-old boy, by two explosions just seconds apart near the finish line.
Police commissioner Ed Davis says 176 victims came to hospitals around Boston, and 17 of those are in critical condition.
Special Agent in Charge Richard DesLauriers says at a news conference there are no known additional threats.
Police commissioner Ed Davis says it is the most complex crime scene in history of the department.
Authorities are looking for amateur video and photographic evidence that can give clues to who set off the bombs.
Suffolk County District Attorney Daniel Conley says "what occurred in Boston was an act of cowardice."
NEIGHBORS REMEMBER 8-YEAR-OLD VICTIM
The young victim of the Boston Marathon bombings is being remembered as a vivacious boy who loved to run and climb.
Eight-year-old Martin Richard was among the three people killed in the explosions Monday. That's according to a person who talked to a friend of the family and spoke to The Associated Press on condition of anonymity. His mother and sister were badly injured.
A candle burned on the stoop of the family's single-family home in the city's Dorchester section Tuesday, and the word "Peace" was written in chalk on the front walkway.
Neighbor Betty Delorey says Martin loved to climb the neighborhood trees, and hop the fence outside his home.
The children's father, Bill, is the director of a local community group. The boy's mother, Denise, works at the Neighborhood House Charter School, where her children attend classes.