The Christmas morning blast in the US city of Nashville caused widespread communications outages which affected police emergency systems and grounded holiday travel at the local airport.
Metro Nashville police chief John Drake said officers had been responding to a report of shots fired early on Friday when they encountered a camper van blaring a recorded warning that a bomb would detonate in 15 minutes.
Police evacuated nearby buildings and called in the bomb squad, shortly before the RV exploded.
After issuing a curfew for the area, Mayor John Cooper said at a news conference: “This morning’s attack on our community was intended to create chaos and fear in this season of peace and hope. But Nashvillians have proven time and time again that the spirit of our city cannot be broken.”
Police believe the blast in the state capital of Tennessee was intentional, but do not yet know a motive or target. Mr Drake noted that officials had not received any threats before the explosion.
The chief said investigators at the scene “have found tissue that we believe could be remains, but we’ll have that examined and let you know at that time”.
Police could not say whether the remains potentially came from someone inside the RV.
Three people taken to hospital for treatment were in stable condition on Friday evening, Mr Cooper said.
Surveillance video published on a Twitter account on Friday that appeared to be across the street from the blast captured the warning issuing from the vehicle, saying: “… if you can hear this message, evacuate now”, seconds before the explosion.
The blast sent black smoke and flames billowing from the heart of Nashville’s tourist scene, an area packed with bars, restaurants and shops.
Buildings shook and windows shattered streets away from the explosion near a building owned by AT&T that lies one block from the company’s office tower, a landmark in the city centre.
“We do not know if that was a coincidence, or if that was the intention,” police spokesman Don Aaron said. He said some people were being questioned in connection with the blast.
AT&T said the affected building is the central office of a telephone exchange, with network equipment in it. The blast interrupted service, but the company declined to say how widespread outages were.
The AT&T outages site showed service issues in middle Tennessee and Kentucky. Several police agencies reported that their 911 systems were down because of the outage, including Knox County, home to Knoxville about 180 miles east of Nashville.
AT&T said that it was bringing in portable mobile sites and was working with law enforcement to get access to make repairs to its equipment. The company noted that “power is essential to restoring” services.
The Federal Aviation Administration temporarily halted flights out of Nashville International Airport because of telecommunications issues associated with the explosion.
Later on Friday, the Metropolitan Nashville Airport Authority said most flights were resuming but advised passengers to check with their airline for updates due to possible delays.
The FBI will be taking the lead in the investigation, agency spokesman Joel Siskovic said.
The agency is America’s primary law enforcement agency responsible for investigating federal crimes, such as explosives violations and acts of terrorism.
President Donald Trump has been briefed, according to White House spokesperson Judd Deere. The US justice department said acting attorney general Jeff Rosen was also briefed and directed all department resources be made available to help with the investigation.
Tennessee’s governor Bill Lee said on Twitter that the state would provide the resources necessary “to determine what happened and who was responsible”.
The American Red Cross of Tennessee announced that it was working with officials to open a shelter for victims.
