A parked camper van exploded in the US city of Nashville, Tennessee, early on Christmas morning, injuring three people and knocking out communications systems across the state, BBC reported. Possible human remains were later found near the blast site, US media reported. Police believe the powerful blast was caused deliberately. Officers responding to reports of gunshots just before 06:00 (12:00 GMT) found a camper van broadcasting a warning message to leave the area. The van exploded a few minutes later. A police officer was knocked off the feet by the force of the blast, officials said. Police have now 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 much of Tennessee. Flights out of Nashville International Airport were briefly halted as a result of damage done by the blast but have now resumed.