NASHVILLE — Investigators were rushing on Saturday to piece together what officials described as an elaborate jigsaw puzzle, chasing hundreds of leads, to identify the culprit and the motivation behind the Christmas Day explosion that rocked Nashville.
Federal officials said on Saturday that the investigation included hundreds of federal agents, who were following up on nearly 500 tips that had been called in since Friday. They said they were still trying to determine whether more than one person was involved.
The authorities have identified a 63-year-old man who apparently owned an R.V. similar to the one in the bombing and were seeking to question him, according to a federal law enforcement official familiar with the investigation.
On Saturday morning, several dozen investigators with the F.B.I. and the Bureau of Alcohol, Tobacco, Firearms and Explosives began searching a brick duplex in Antioch, a neighborhood in the Nashville area. An image of the building from May 2019, captured on Google Street View, shows an R.V. in the yard that appears similar to the one that the authorities say is at the center of the explosion.
“Our investigative team is turning over every stone,” Douglas Korneski, the special agent in charge of the F.B.I. field office in Memphis, said in a news conference on Saturday, “to make sure we know as many details as possible to answer the question of who is responsible for this, and also to understand why did they do this.”
In Nashville, a several-block area was closed off in a search for evidence on Saturday. Officials said that they were aware of no other explosive threats and that the search so far had not uncovered any other devices in the area.
“It is like a giant jigsaw puzzle created by a bomb that throws pieces of evidence across multiple city blocks,” Donald Q. Cochran, the U.S. attorney for the Middle District of Tennessee, said during the Saturday briefing. “They have got to gather it, they have got to catalog it, put it back together.”
The explosion came on Friday morning after Nashville police officers responding to a complaint about gunfire encountered an R.V. parked on Second Avenue North blaring a message that a bomb was about to detonate. The blast rippled across several blocks, blowing windows and even causing one building to collapse, and it left Nashville rattled and perplexed.
The authorities said that the explosion had the potential to inflict enormous carnage, had it detonated at a time other than early on a quiet holiday morning and without a warning that led police officers to clear away as many people in surrounding buildings as they could. Three people were hospitalized. Police officials said there were no indications of fatalities, but possible human tissue had been found amid the debris.
But the blast caused considerable disruption, as it damaged a critical piece of the broader area’s telecommunications infrastructure. The authorities were also forced to cordon off a large section of downtown, displacing dozens of people and leaving business owners unable to reach their shops and offices.
One of the major lines of inquiry was whether there was significance in the location of the blast: on a downtown street in front of an AT&T transmission building. The explosion created significant damage to the facility, causing widespread repercussions to telecommunication systems in Nashville and beyond. Officials said the outages have affected 911 operations and flights at Nashville International Airport. Across the region, residents and businesses lost cellphone service and internet connections, and many were still experiencing issues on Saturday.
AT&T has installed portable cell sites in downtown Nashville to alleviate some of the outages, the company said. Workers were drilling access holes into the building and trying to restore power to equipment essential to resuming service.
“Challenges remain, including a fire which reignited overnight and led to the evacuation of the building,” the company said in a statement on Saturday. And in a previous statement, AT&T officials said, “There are serious logistical challenges to working in a disaster area and we will make measurable progress in the hours and days ahead.”
The explosion affected some cell service across parts of Tennessee, Kentucky and Alabama, and hindered the communication of 20 or more 911 call centers, Gov. Bill Lee of Tennessee said.
The Federal Aviation Administration temporarily halted flights out of the Nashville International Airport because of telecommunications issues caused by the blast. The F.A.A. also labeled the skies within about one mile of the blast “national defense airspace,” meaning pilots are prohibited from flying overhead without special authorization.
On the day after Christmas, shoppers at some retail outlets had to pay with cash or checks as sellers could not access credit card systems. Cash-only sales were reported by shoppers in Dickson and Franklin, Tenn., at national retailers like Walmart and Old Navy.
At M.L. Rose, a bar and restaurant in the Capitol View neighborhood near downtown, the lack of internet forced the business to rely on a backup, offline system because of an inability to process cards. Restaurants like Dino’s, a favorite East Nashville dive and burger joint, went cash only and canceled takeout orders, something they have relied upon as the coronavirus pandemic has limited indoor seating.
It could take days before service is fully restored, officials said.
“It is a big operation with the building itself,” William Swann, the chief of the Nashville Fire Department, said at the news conference on Saturday. “We are trying to at least get the generators back in order so that the mobile phones can be back in operation.”
In Antioch, roughly 11 miles from the site of the explosion, federal agents swarmed one of the units in a complex of matching duplexes, all while children played tag outside nearby homes and neighbors watched the investigators work. The home had been cleared by swat and bomb teams to ensure it was safe.
On Saturday morning, Mr. Lee, a Republican, toured the scene of the explosion and shared a letter he wrote to President Trump asking him to declare an emergency disaster for Tennessee and send federal aid to help recover, given the “severity and magnitude” of the destruction.
At least 41 buildings sustained damage in the blast. At a hostel near the site, security cameras captured footage of the explosion blowing in the front doors of the building, which was filled with dust and debris. More than a day later, the water from sprinklers had not been shut off.
The explosion added to what has already been a devastating year: The Nashville Downtown Hostel largely caters to international vacationers, especially youth travelers, and has suffered an 80 percent drop in revenue from 2019 because of the coronavirus pandemic.
“All of that space has been flooding since the bombing,” said Ron Limb, who owns the hostel and who has not been able to gain access to the business. “It’s been running for 28 hours.”
“For the first six to twelve hours,” he went on, “I was trying to be very patient because it’s such a big emergency. The blast did some damage to the building, but I’m literally watching my building and my business get flooded away.”
Rick Rojas and Steve Cavendish reported from Nashville, Giulia McDonnell Nieto del Rio from New York and Nicholas Bogel-Burroughs from Edisto Island, S.C. Jamie McGee contributed reporting from Nashville, Adam Goldman from Washington and Alain Delaquérière contributed research.