Two days after explosives killed three people and wounded more than 180 during the Boston Marathon, details continue to trickle in as investigators sort through evidence. Authorities will hold a news conference at 1 p.m. ET.
-- A lid to a pressure cooker, thought to have been used in the bombings, was found on a roof near the scene of the blasts, a federal law enforcement official with knowledge of the investigation tells CNN.
The blasts left three people dead.
-- Martin Richard, an 8-year-old boy with a gap-tooth grin and bright eyes. He loved to run and play in his yard.
-- Krystle Campbell, a 29-year-old freckle-faced woman described by her mother as having "a heart of gold."
-- The third fatality was a Chinese graduate student at Boston University who had moved to the city last fall.
The explosions wounded 183 people.
-- At least 100 have been released from area hospitals, according to a CNN tally.
-- Martin's mother and sister are among the wounded. His mother underwent surgery for a brain injury, and his 6-year-old sister lost her leg.
-- Doctors say dozens of victims suffered injuries to their legs that involve blood vessels, bone and tissue.
-- The bombings resulted in at least 13 amputations and left doctors picking ball bearings out of victims in the emergency room, a terrorism expert briefed on the investigation said.
-- The two bombs hit 12 seconds apart near the marathon's finish line.
-- One of the two bombs was housed in a pressure cooker hidden inside a backpack, the FBI said. To maximize the impact of the shrapnel, the device may have included "nails, BBs and ball bearings."
-- The second bomb was also in a metal container, but there's not enough evidence to determine whether it too was in a pressure cooker, the agency said.
-- Evidence recovered from the scene will be sent to the FBI's lab in Quantico, Virginia, where analysts will attempt to reconstruct the devices used in the attack.
Pressure cooker bombs
-- The simplicity of the bomb makes it hard to trace it to any particular group, an official said.
-- The "recipe" for the bombs ignited by pressure cookers can be found widely on the Internet.
-- In 2004, Homeland Security issued an advisory about pressure cooker bombs.
-- They are made by placing TNT or other explosives in a pressure cooker and attaching a blasting cap at the top, the advisory said. Pressure cooker bombs are made with readily available materials.
-- Though it could indicate domestic terrorism, such bombs have been used in a handful of instances related to international terrorism attempts over the last few years, an official said.
Terror group links
-- No connection has been made to any terrorist group or individual.
-- "There is no reporting indicating a foreign connection, or any reaction from al Qaeda," a senior U.S. official said.
-- President Barack Obama described the bombings as an act of terrorism, but said it is unclear whether they were the work of a group or "a malevolent individual."
-- The Pakistani Taliban has said it was not involved in the attack.
-- Authorities don't have a sense of what the motive is, and no one is in custody, an official said.
-- Richard DesLauriers, the special agent in charge of the FBI's Boston office, asked the public to report anyone who talked about targeting the marathon or showed interest in explosives. He urged anyone who might have heard explosions in remote areas -- possibly by someone testing a bomb -- or seen someone carrying "an unusually heavy, dark-colored bag" around the time of the attack to come forward.
-- Obama received updates overnight about the investigation, a White House official said.
-- White House officials have been briefed by senior members of the federal response and law enforcement team over the past two days.
-- Attorney General Eric Holder, FBI Director Robert Mueller, Homeland Security adviser Lisa Monaco and other senior members of his team will brief Obama Wednesday.
-- Authorities are processing "the most complex crime scene that we have dealt with in the history of our department," said Ed Davis, the Boston police commissioner.
-- Forensic specialists and dogs trained to detect explosive devices and their residue were at the scene of the blasts. A command post has been created, with 1,000 officers conducting interviews and gathering details.
-- Authorities have received 2,000 tips from around the world, said DesLauriers, the FBI agent. "Someone knows who did this," he said.
No Saudi connection
-- U.S. officials have said that more than one Saudi has been interviewed, including a 20-year-old student who was questioned as a possible witness.
-- But a U.S. official said the student "was just in the wrong place at the wrong time."
-- The Saudi Embassy in the United States said no Saudi appears to have been involved.
"The embassy stresses that there is no evidence, according to U.S. authorities, of involvement of any Saudi national in the bombings," it said Tuesday in a statement.
-- The investigation is inconclusive.
"They thought they had something with the Saudi national, and that evaporated," a senior law enforcement official said. "There's no sense that they have latched onto anybody or any motive."
-- Authorities are asking those who may have video or pictures taken of the scene around the time of the blasts to call city or FBI hot lines.
-- Cities have stepped up security after the attacks, including Washington, New York, Miami, Chicago and Los Angeles.
-- British police said they are reviewing the security plan for the London Marathon scheduled for Sunday. The marathon will mark 30 seconds of silence and is urging runners to wear a black ribbon to mark the Boston tragedy.
-- Crowds gathered for a vigil on the Boston Common on Tuesday night. They sang songs and lit candles, some wept.
-- In New York, the Yankees played "Sweet Caroline" during their game against the Arizona Diamondbacks in a tribute to the victims. The Boston Red Sox team has played the Neil Diamond song during its games for the past 15 years.
-- Obama will travel to Boston on Thursday for an 11 a.m. interfaith service dedicated to the victims.
-- CNN"s Faith Karimi wrote this report from information provided by CNN staffers.
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