By MEREDITH DELISO and AARON KATERSKY, ABC News

(NASHVILLE, Tenn.) — Authorities are looking at a “number of individuals” and do not believe there is another subject as they investigate an explosion that rocked downtown Nashville on Christmas.

Law enforcement agencies have received nearly 500 tips after a parked recreational vehicle exploded Friday morning, causing extensive damage.

“We are continuing to follow every lead we have,” U.S. Attorney Don Cochran said during a press briefing Saturday afternoon.

FBI agent Doug Korneski declined to confirm if a person of interest has been identified, but he said the FBI is “not looking for another subject.”

“There are a number of individuals that we’re looking at,” Korneski said. “At this point, we’re not prepared to identify any single individual.”

There are no known additional explosive threats at this time, authorities said.

“Nashville is safe,” Metro Nashville Police Chief John Drake said during the briefing. “We feel and know that we have no known threats at this time against our city.”

Authorities urged people to avoid the area, as a curfew is in effect until Sunday afternoon.

Drake asked residents and business owners to “be patient” Saturday while the investigation is underway.

“Just know that your businesses are safe,” Drake said in a video address Saturday afternoon. “We have law enforcement officers at each corner to protect the area, so no one will be allowed access into your business.”

Announcements coming from an RV said a potential bomb would detonate within 15 minutes, police said, before it exploded around 6:30 a.m. Friday, blowing out the windows of nearby buildings. The explosion is believed to have been an intentional act, authorities said.

Officers worked to evacuate nearby buildings before the explosion. The department identified them Friday night as Officer Brenna Hosey; Officer James Luellen; Officer Michael Sipos; Officer Amanda Topping; Officer James Wells; and Sergeant Timothy Miller.

The officers were lauded as heroes during a press conference Friday, as they “took swift action and directed people away from danger,” Nashville Mayor John Cooper said.

“The officers saved lives today,” Drake also said. “They immediately began knocking on doors, not knowing if the bomb was going to go off immediately. They didn’t care about themselves, they didn’t think about that, they cared about the citizens of Nashville.” . Tennessee Gov. Bill Lee also praised the “swift action” of Nashville police and local law enforcement after touring the site of the explosion Saturday morning.

“The damage is shocking and it is a miracle that no residents were killed,” he said on Twitter.

Three people were taken to the hospital with minor injuries. Human remains were found at the scene, multiple law enforcement sources told ABC News. The remains have not been identified as of Saturday afternoon.

Multiple buildings on Second Avenue were damaged, some extensively, authorities said.

Gov. Lee said he has requested an emergency declaration from President Donald Trump “to support ongoing efforts and relief.”

The vehicle exploded outside an AT&T transmission building. Service continues to be impacted in Nashville and surrounding areas because of damage to its facilities.

A fire reignited overnight, leading to the evaluation of the building, AT&T said in a statement Saturday morning. Teams have drilled holes into the building in an attempt to reconnect power to critical equipment, and are also rerouting services to other facilities in the area, it said.

The company has set up two portable cell sites in downtown Nashville, “with numerous additional portable sites being deployed in the Nashville area and in the region,” it said.

The Federal Aviation Administration has issued a temporary flight restriction for Nashville, classifying the airspace as National Defense Airspace. Pilots who do not follow the restriction could be detained, the FAA warned.

The FBI and the U.S. Department of Justice’s Bureau of Alcohol, Tobacco, Firearms and Explosives are leading the investigation. The FBI has fielded nearly 500 tips as of Saturday afternoon, authorities said.

The FBI is asking anyone with information to submit a tip on its website.

ABC News’ Josh Hoyos, Ahmad Hemingway and Sam Sweeney contributed to this report.

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