Authorities in Nashville on Saturday probed an explosion that ripped through part of the US city on Christmas morning after a chilling bomb warning while the governor requested an emergency declaration from the White House.
The explosion of a motorhome at 6:30 am (1230 GMT) on Friday in historic downtown Nashville, the United States' country music capital, damaged dozens of businesses and injured at least three people, with the streets largely abandoned at that hour.
No deaths have been confirmed but authorities were examining tissue found at the blast site that they believe could be human remains.
"This morning I toured the site of the bombing," Tennessee Governor Bill Lee said on Twitter on Saturday.
"The damage is shocking and it is a miracle that no residents were killed."
He asked President Donald Trump to declare a state of emergency, a technical move that triggers federal assistance in repairing damage.
At least 41 businesses were damaged, he said.
"These buildings, many of which are historic, and others will need to be assessed by an engineer for structural integrity and safety," Lee said in his request.
The motorhome was parked in front of a building for phone company AT&T, causing damage that disrupted telecommunications service in Tennessee as well as parts of Alabama and Kentucky.
AT&T said Saturday that two portable cell sites were operating in downtown Nashville and additional portable sites were being deployed in the region to restore service.
Nashville's international airport had temporarily halted flights on Friday due to "telecommunications issues" associated with the blast.
Federal and local law enforcement were investigating the explosion and the motive remained unclear.
According to a timeline provided by the governor, police were called to the area to respond to gunfire at 5:30 am, and officers spotted the motorhome at 6.00 am.
Fifteen minutes later, they heard an audio countdown coming from the vehicle warning of a bomb and the need to evacuate, followed by the blast at 6.30 am.
Police have not determined if anyone was inside the motorhome at the time.
Nashville police spokesman Don Aaron said "we do believe that the explosion was an intentional act," while adding that it was unclear if the AT&T building was the target.
Police published a photo of the motorhome on Twitter before it exploded and asked the public for information on it.