Boston Marathon Bombing Investigation Contiunues [VIDEO]

The search continues in and around Boston for whoever planted two bombs at the finish line of the Boston Marathon that killed three and left 144 injured.

Police and federal officials exit an apartment complex at 364 Ocean Avenue in Revere, Mass. with a possible connection to the earlier expolsions during the Boston Marathon (Darren McCollester/Getty Images)

WBZ TV reports that Massachusetts State Police converged on an apartment in nearby Revere but would not say why or what they were looking for other than to say it is in connection with the bombings. Investigators were seen leaving with brown paper bags, plastic trash bags and a duffel bag.

Police also questioned a 20-year-old man Brigham and Women's Hospital but he is not considered a suspect.

Federal investigators said no one had claimed responsibility for the devastating attack on one of the city's most famous civic holidays, Patriots Day. Two explosive devices went off within 15 seconds of each other in the finish line area in Copley Square at 2:45 p.m. following the running of the Boston Marathon.

U.S. Rep. William Keating, a member of the congressional Homeland Security Committee, says the twin bombs appear to be a coordinated attack according to WCVB TV.

But the blasts raised alarms of another terror attack in the U.S. after the explosions at a public event among crowds of thousands of spectators.

Those who work in Boston are encouraged to report as usual but should expect heightened security and checkpoints. The MBTA subway will not be stopping in Copley Square. Flights are coming in-and-out of Boston's Logan Airport as usual but tonight's Celtics game at Boston Garden against the Indiana Pacers has been cancelled.

New Englanders who already had a tax-filing deadline of today because of the Patriot's Day holiday will not have to file by today. Further details will be announced by today.

The American Red Cross in Boston is not calling for blood donations to help victims. "There is currently enough blood on the shelves to meet demand," tweeted @RedCross.

Heightened Security In New Jersey

Boston Marathon explosion (Twitter)

New Jersey's bridges and tunnels are on heightened alert but the FBI says there has been no specific threats made. "The New Jersey State Police has recalled and pre-deployed our bomb unit, aviation crews, tactical teams, and search and rescue assets," Lt. Stephen Jones, a department spokesman, said in a statement.

"NJ Transit police have deployed both uniformed and plain clothed officers to further patrol our system and keep our customers safe," the organization said in a statement, asking riders to be aware of suspicious activity.

Increase In Security

Ben Revere of the Philadelphia Phillies has a message on his gloves during the game agianst the Cincinnati Reds (Andy Lyons/Getty Images)

A surge of security from coast-to-coast and across the Atlantic has followed the Boston Marathon bombings. Security intensified at the White House, New York's Times Square, and in London ahead of former Prime Minister Margaret Thatcher's funeral in London. The London Marathon is also scheduled this weekend. Police in Los Angeles, Washington, D.C., Detroit, San Diego and Las Vegas monitored landmarks, government buildings, transit hubs and sporting events.

The London Marathon will go on as scheduled. Sports Minister Hugh Robertson tells the BBC he is "absolutely confident" the race will be run on Sunday. "This is one of those instances where the best way to show solidarity with Boston is to continue," he added.

The FBI is aware of the significance of April on the calendar. Yesterday was Patriots Day in Massachusetts and also the day federal income tax forms needed to be filed. 100 were killed in April, 1993 in the FBI's siege of a compound in Waco, Texas while in April, 1995 nearly 200 were killed in the bombing of a federal building in Oklahoma City.

FULL COVERAGE: Boston Marathon Explosion

The Associated Press contributed to this story