"It works on Boston Harbor water, on Charles River water, anything, " says Metcalfe.

FORBES: Cheap Hydrogen From Dirty Water...Maybe

Ziedonis Barbaks, from a group called the Latvian Community of Boston Stronger Together, believes the protest will not solve anything.

BBC: Concern over immigration protest in Boston, Lincolnshire

Has the FBI told the White House anything about whether the letters that have been received are related to the Boston incident?

WHITEHOUSE: Press Briefing

At an initial news conference, Boston Police Commissioner Edward Davis said authorities had received "no specific intelligence that anything was going to happen".

BBC: Boston Marathon hit by deadly twin explosions

"There was no specific intelligence that anything was going to happen, " Mr. Davis said at an evening news conference in Boston.

WSJ: Two Explosions at Boston Marathon Finish Line

"I'm not talking about anything ahead of Game 5, " the Pittsburgh captain said when asked about a potential Eastern Conference final against the Boston Bruins.

NPR: Penguins Rout Senators 7-3, Take 3-1 Series Lead