A blast which shook the US city of Nashville, Tennessee early on Christmas morning is believed to be deliberate and linked to a vehicle, police say.
Three people were taken to hospital, the fire department said, but none of them are thought to be critically hurt.
Smoke was seen rising above the city centre after the explosion at about 06:30 (00:30 GMT) on Friday.
The FBI and investigators from the Bureau of Alcohol, Tobacco, Firearms and Explosives are at the scene.
No cause has yet been identified.
A police spokesman told a hastily convened news conference that the force received reports of gunshots at about 06:00. When the bomb squad went to the scene, officers found a suspicious vehicle. A short time later, the vehicle exploded.
It was not clear whether anyone was inside the vehicle at the time of the explosion, police said.
Images from the scene showed blown-out windows and felled trees.
“It looks like a bomb went off,” Nashville Mayor John Cooper said.
US President Donald Trump has been briefed on the matter.