Security will be tighter than ever in several US cities during Independence Day celebrations this week, which will see some of the largest public gatherings in the country since the deadly Boston Marathon bombings in April.
Security officials said they would deploy record numbers of police, install scores of new surveillance cameras and search checkpoints at fireworks displays, concerts and other Fourth of July events in Boston, New York, Washington and Atlanta.
The National Explosives Task Force has urged fireworks sellers in the US to report buyers who raise suspicion, according to an industry advisory.
The Boston Marathon bombers had used materials from fireworks bought at a store to build bombs, as had a man convicted of attempting to bomb Times Square in New York in 2010.
"The increase (in security) is, of course, related to the Marathon bombing and other global events," said David Procopio, a spokesman for the Massachusetts State Police, noting that Boston's Independence Day events were reportedly the Boston bombers' initial target.
Three people were killed and 264 injured when two pressure-cooker bombs, loaded with shrapnel and fireworks-grade gunpowder, exploded at the finish line of the Boston Marathon April 15, in the biggest attack on American soil since the September 11, 2001 attack on New York's World Trade Center towers.
Tamerlan and Dzhokhar Tsarnaev, the two brothers suspected of carrying out the attack on the marathon, had originally planned to set off their homemade bombs on July 4, but attacked earlier because they had made the devices sooner than expected, law enforcement officials have said.
Boston's Independence Day events include concerts and a fireworks display along the city's waterfront that traditionally attracts a half million people.
A federal indictment says Tamerlan - who was killed in a shootout with police days after the bombing - purchased 48 mortars containing some eight pounds of low-explosive gun powder from a fireworks store in New Hampshire in February.
Dzhokhar is in jail awaiting trial on charges including murder and using a weapon of mass destruction. He could face the death penalty if convicted.
Massachusetts State Police Commissioner Timothy Alben said the state will deploy record numbers of uniformed and undercover cops, install a 'significant' number of new surveillance cameras, boost boat patrols, and ban items like backpacks and large coolers at the events.
"Please be assured that the steps ... are not the result of any specific threat to this event. We have no intelligence of any such threat," he said.
Massachusetts officials have declined to provide additional details of the security measures, but said they were the result of collaboration with other police departments with counter-terrorism experience, including those in New York and London.
Police officials in New York and Washington also said they were tightening security.
"Coverage includes large numbers uniformed and plain clothes police officers, police helicopters and boats, additional mobile cameras, radiation detection, and street checkpoints," said Paul Browne, Deputy Commissioner of the New York City Police Department.
In Atlanta, where there will be a Fourth of July fireworks display and an annual Peachtree Road Race, officials said the entire police force would be working, and surveillance along the race course would be increased.+
"There should not be a single spot on the route that does not have camera coverage," Atlanta Police Chief George Turner said. "The specter of what happened in Boston with the marathon on April 15 weighs heavily on our hearts and minds."