US investigators have appealed to the public for information as they posted a photo on social media of a recreational vehicle that exploded in Nashville, in the state of Tennessee, early on Christmas morning.
Three people suffered injuries in the Friday morning blast in the normally busy downtown of the state's capital. Debris was scattered across a wide area, with many buildings damaged and several vehicles burned out.
The incident affected nearby communications, causing flight operators to delay departures at the city's airport.
Local police and the FBI continue to investigate the case. The vehicle was reportedly parked at the location for five hours before the incident.
Police say a warning of an imminent explosion was heard coming from the vehicle immediately before the blast.
Police say they have found what could be human tissue at the scene, and are looking into its possible connection with the case.
The area is in a shopping district with many restaurants and bars, but there were few pedestrians on Christmas morning.