Officials in the US state of Tennessee said the DNA matched that of Anthony Quinn Warner, 63.

The FBI said there was no indication of additional suspects and that it was too early to suggest a motive.

The blast outside a telecoms office disrupted communications systems in Tennessee and four other states.

During a press conference on Sunday, federal investigators said they believed that Warner, who worked in IT and had extensive experience with electronics, was the sole individual responsible for the blast and had died at the site.

They said the blast was probably deliberate, and that it was Warner's remains discovered at the scene.

According to public records, Warner had until recently lived in Antioch, a suburb of Nashville, where police searched a home on Saturday.

Neighbours also reported seeing a camper van at the premises, local media report.

Earlier, CBS News reported that a DNA sample had been collected from Warner's mother.

FBI Special Agent in Charge Douglas Korneski said officials had received about 500 tips relating to the explosion.

"We're still following leads but right now there is no indication that any other persons were involved," he said. "We reviewed hours of security video surrounding the recreation vehicle which saw no other people involved."

Public records cited by US media show Warner had wide experience with electronics and alarm systems.

He was a long-time resident of Nashville and had worked as a freelance computer technician with an estate agency.

His former employer, estate agent Steve Fridrich, told the Nashville Tennessean that Warner had resigned unexpectedly this month after four years with the company. Mr Fridrich said the move had been "quite out of character".

A neighbour in Antioch described Warner as "a computer geek", USA Today reported.

Steve Schmoldt, who lived next door to Warner for more than two decades, described him as "friendly" and "low key", adding: "I guess some people would say he's a little odd."

"You never saw anyone come and go," the newspaper quoted him as saying. "As far as we knew, he was kind of a computer geek that worked at home."

Mr Schmoldt said Warner gave no indication of having held strong political beliefs.

"He never had any yard signs or flags in his window or anything like that," he said.

Officers responded to reports of gunshots just before 06:00 local time (12:00 GMT) on 25 December in an area of the city known for its restaurants and nightlife.

Shortly afterwards, they found a camper van broadcasting a warning message to leave the area.

Police said the van had also broadcast the 1964 hit song Downtown by British singer Petula Clark, the Tennessean newspaper reported.

The van exploded a few minutes later, the force of the blast knocking an officer off their feet, police said.

Police have released this image of the van - described by Nashville police as a recreational vehicle (RV) - arriving at the scene early on Friday.

The van blew up outside a building belonging to the telecoms giant AT&T, which also occupies an office tower nearby.

Buildings suffered structural damage, windows were blown out, and trees were felled. Videos posted on social media showed water from damaged pipes running down walls as alarms howled in the background.

Police emergency systems were knocked out across Tennessee.

Telephone, internet and fibre optic TV services were also disrupted in Tennessee, Mississippi, Kentucky, Alabama and Georgia, according to AT&T.

Resident Buck McCoy said he had been woken up by the blast. He posted a video on Facebook, showing some of the damage done, with alarms howling in the background.

"All my windows, every single one of them got blown into the next room. If I had been standing there, it would have been horrible," Mr McCoy told AP. "It felt like a bomb. It was that big."