President Barack Obama was due to visit Boston on Thursday to attend a memorial service for victims of the Boston Marathon bombing amid a manhunt for a suspect seen on video taken before two blasts struck near the finish line on Monday.
Obama will address an interfaith service and by extension the country following the blasts that killed three people and wounded 176 in the worst attack on U.S. soil since Sept. 11, 2001.
The president also leaves a capital city that was abuzz on Wednesday after the U.S. Federal Bureau of Investigation (FBI) arrested a Mississippi man in connection with letters sent to Obama and two other officials that were believed to have contained the deadly poison ricin.
The FBI said there was no indication of a connection between the ricin letters and the Boston bomb attacks, but they reminded Americans of anthrax mail attacks in the wake of the Sept. 11 suicide hijackings 12 years ago.
Investigators believe the Boston bombs were fashioned out of pressure cookers and packed with shrapnel. Ten victims lost limbs and emergency room doctors reported plucking nails and ball bearing from the wounded.
No arrests had been made, and the suspect in the video had not been identified by name, two U.S. government officials said.
Police had considered making an appeal to the public for more information at a news conference on Wednesday, a U.S. government source said, but the FBI canceled that news conference after a number of delays.
The bombs in Boston killed an 8-year-old boy, Martin Richard; a 29-year-old woman, Krystle Campbell, and a Boston University graduate student and Chinese citizen, Lu Lingzi.
The crowded scene along the race course in central Boston on Monday was recorded by surveillance cameras and media outlets, providing investigators with significant video of the area before and after the two blasts.
Based on the shards of metal, fabric, wires and a battery recovered at the scene, the focus turned to whoever may have placed homemade bombs in pressure cooker pots and taken them in heavy black nylon bags to the finish line of the world-famous race watched by thousands of spectators.
Amid an outpouring of public support for the victims, Kenneth Feinberg, the attorney who oversaw compensation funds for victims of the Sept. 11 attacks and the April 2007 Virginia Tech shootings, was named to administer a fund for those affected by the Boston bombing.
Feinberg, a leading expert on disaster compensation, will serve as administrator of the One Fund Boston, Governor Deval Patrick and Mayor Thomas Menino said in a statement. The fund, unveiled on Tuesday, was seeded with a $1 million donation from the financial services firm John Hancock.
The fund was up to $7 million on Wednesday, its sponsors said, including donations from more than 8,500 people.