A massive explosion rocked downtown Nashville, Tennessee, on Christmas morning, an incident that caused destruction for several blocks and is being called "intentional" by authorities.
Here's what we know about the incident:
Nashville explosion location, what happened
Nashville police and fire crews responded to reports of a suspicious RV parked outside an AT&T building near Second Avenue and Commerce Street just before 6 a.m. Friday.
Upon arrival, police said an officer "had reason" to alert the department's hazardous devices unit, which was en route, when a "significant explosion" happened.
Police and firefighters responded to the area about 6:45 a.m.
As of Friday evening, Metro police Chief John Drake said a motive in the explosion was not known.
Drake said it was unclear if anyone was inside the RV when it exploded.
Officers and witnesses heard a broadcast coming from the RV giving a dire warning: “Evacuate now. There is a bomb. A bomb is in this vehicle and will explode."
He said police found tissue at the scene that could be human remains. Authorities will examine it to determine what it is.
NASHVILLE EXPLOSION:Nashville residents capture confusion, chaos in moments after downtown explosion
MNPD releases photo of RV linked to explosion
The investigation around the explosion has focused on an RV that was in the area Friday morning.
Police released a surveillance photo of the RV Friday afternoon and asked for the public's help.
Police said the RV in question was spotted in the area of Second Avenue North and Commerce Street after 1 a.m. Friday.
At least one witness in the area described a chilling warning that emanated from the RV before the explosion took place.
Police confirmed they believe the announcement came from the vehicle.
Downtown closed, curfew started
All downtown Nashville roads, including interstates leading into the city, are shut down.
The downtown area will be "sealed off" for further investigation and to make sure everything is "completely safe," according to Nashville Mayor John Cooper.
Cooper on Friday afternoon announced he was asking Gov. Bill Lee to issue a state of civil emergency at the explosion site and the surrounding area, that will put in place a curfew starting Friday at 4:30 p.m. until Sunday 4:30 p.m.
Injuries were reported
Just before the blast, officers were conducting door-to-door checks in the area and redirected a man walking his dog along the street.
The force of the explosion knocked an officer to the ground.
At least three people were hospitalized, authorities said. All three individuals were in stable condition, Cooper said.
The identities of those hurt and the extent of their injuries was not immediately known.
Six Central Precinct officers were at the scene. Cooper called them heroes.
Businesses damaged, homes destroyed
Cooper toured the damage Friday morning and said at an evening press conference at least 41 businesses in the area had been damaged in connection to the explosion.
"It looks like a bomb went off," Cooper said Friday morning.
Cooper declared a state of civil emergency late Friday afternoon.
Fire Chief William Swann said one building collapsed and others sustained major damage in the area around where the blast went off.
Several downtown residents' homes were destroyed, Swann said.
The American Red Cross opened a shelter for those who were displaced, he said.
AT&T outage linked to Nashville bombing
A widespread internet outage was reported in Nashville hours after the massive explosion downtown.
AT&T internet and phone service were disrupted in the area about 12 p.m. Friday.
Users around the country reported disruptions in service, but there was a concentration in the Nashville area and Middle Tennessee. A handful of Middle Tennessee police departments reported the outage was disrupting 911 access in their jurisdictions.
Nashville International Airport halted flights out of the area temporarily on Friday afternoon.
The outages were reported several hours after an explosion in downtown Nashville that took place near an AT&T facility.
An AT&T spokesman confirmed the outage was linked to the explosion:
"Service for some customers in Nashville and the surrounding areas may be affected by damage to our facilities from the explosion this morning. We are in contact with law enforcement and working as quickly and safely as possible to restore service," said Jim Greer, an AT&T representative.
Multiple law enforcement agencies are on scene
Metro police, the Tennessee Bureau of Investigation, ATF and the FBI are investigating the incident.
The Nashville Fire Department said a bomb squad was also on scene.
Multiple people questioned
Several people were taken to the department's central precinct for questioning but authorities declined to give more details Friday morning.
As of 3 p.m. no suspect information had been released.
Reward offered for information
The Nashville Convention & Visitors Corp announced Friday afternoon a $10,000 contribution toward a reward in the case.
The Nashville Convention & Visitors Corp. said it invited other hospitality businesses to contribute to a reward in the case. As of Friday evening it had grown to $31,000.
Anyone with information is asked to call (615) 862-7400.