Debris litters the road near the site of an explosion in the area of Second and Commerce in Nashville, Tennessee, U.S. December 25, 2020.Elliott Anderson | via ReutersInvestigators have received more than 500 tips about the Christmas morning explosion in Nashville but have not determined the identity of the bomber, officials said Saturday afternoon.Local law enforcement is working with federal agencies, including the Federal Bureau of Investigation and the Bureau of Alcohol, Tobacco, Firearms, and Explosives, to investigate the blast site, which encompasses dozens of businesses in the city.”That’s the stage that we are at in this investigation. We are still continuing to follow every lead that we have, and we will continue to do so until we find out what’s happened,” said Don Cochran, the U.S. Attorney for the Middle District of Tennessee.The explosion in downtown Nashville early Christmas morning shattered windows and knocked out communications networks. Authorities said they believe the explosion was intentional and came from an RV parked on the street.According to the FBI, the RV arrived in the area shortly after 1 a.m. local time, and the explosion occurred around 5:30 a.m. A warning for citizens in the area to evacuate blared from the RV before the blast.Doug Korneski, the FBI’s special agent in charge for the Memphis Field Office, said Saturday that there is no indication of a continuing bomb threat in the area. When asked about reports that investigators have identified a person of interest in the case, Korneski said the investigation was still looking at several individuals.Metro Nashville Police Chief John Drake said on Friday that there were no known fatalities from the blast, though police were testing tissue found at the scene to determine if it could be human remains, according to NBC News. Korneski said investigators are still examining the tissue.Nashville Mayor John Cooper has issued a curfew for part of downtown that runs through Sunday afternoon. Federal regulators briefly halted flights into the city on Friday as the investigation began.Social media users have reported issues with phone and internet service in Nashville following the blast. AT&T said on Saturday morning that it is deploying portable cell sites in the area in an attempt to restore coverage quickly.