Boston 'Not Taking Any Chances' on July 4 Security

July 3, 2013 — -- Authorities said they are unaware of a specific terror threat to the nation's July 4 celebrations, but in Boston security officials "are not taking any chances" following the marathon bombing there just weeks ago, Boston Police Commissioner Ed Davis told ABC News today.

Another top Massachusetts law man, State Police Col. Tim Alben, told reporters that at this year's festivities, "It will be evident that security has changed quite a bit" for Boston's annual Independence Day extravaganza.

"After April 15, things changed around the country," Alben said.

On April 15 this year a pair of bombs exploded near the finish line of the Boston Marathon, killing three people and injuring more than 260 others. Authorities later learned that the suspects in that case, two brothers apparently inspired by al Qaeda, had first planned to strike at Boston's famed July 4 celebration and only accelerated their timeline after building their explosives.

FULL COVERAGE: Boston Marathon Bombing

Law enforcement officials were quick to point out today there have been no other direct threats made against Boston's annual event, and ABC News obtained an FBI-Department of Homeland Security bulletin that said so far there was no "specific, credible information" about threats against any American city.

Still, the bulletin noted that any July 4 celebration would make for "potentially attractive terrorist targets due to the presence of large crowds, the potential ease of access to locations hosting holiday events, and the symbolic nature of the holiday."

READ: No 'Specific, Credible' Threat Known for July 4

Boston's finest are taking the alleged Boston bombers' original plan as a warning.

Alben spoke to reporters today at the city's clandestine Uniform Command Center, which is tuned into the city's sophisticated system of security cameras and police officers that will monitor the entire event from the room.

"I want people to feel like this is a safe place to come,'' Alben said, adding that his own family will be in attendance.

Among the security-minded changes this year is the city's decision, for the first time in 25 years, not to nationally broadcast the spectacle from Boston's Esplanade. There will be dozens of uniformed and plain clothes police officers in the city, who will in turn be bolstered by Secret Service agents as they mill through the throngs of attendees.

For the first time the perimeter of the Esplanade is ringed with barriers so no one can access that area of the celebration without being screened by security positions at checkpoints along the Charles River. State Police divers have been searching the water, bomb squad officers from across the state have been sweeping the entire area, and helicopters will be hovering overhead with infrared cameras trained on the crowd.

The weeks after the Boston Marathon attacks have been straining, police said. The State Police bomb squad has responded to more than 200 911 calls for possible devices and have raced to 20 different bomb threats, according to Col. Frank Matthews, Commander of Division of Investigative Services. Bomb-sniffing dogs have conducted over 150 security sweeps.

The BPD has also been strained with an uptick in homicides in the city and the increased pressure of terrorism prevention. In fact, Davis said he will be splitting his time between the Esplanade and Mattapan, a neighborhood hard hit by gunfire.

"We want to make sure everyone in the city is safe, not just the people celebrating with the Pops,'' he told ABC News, referring to the orchestra.

Michele McPhee is a Boston-based freelance writer and frequent contributor to ABC News.