Officials believe that a Christmas morning explosion in downtown Nashville was an intentional act, according to a Metro Nashville Police spokesman.

In a brief news conference Friday morning, spokesman Don Aaron said the department's hazardous devices unit was headed downtown in response to a call about a suspicious vehicle when there was a “significant” explosion linked to that vehicle around 6:30 a.m. CT.

“We do believe that the explosion was an intentional act,” Aaron said.

Three people have been transported to hospitals form the scene, but none are in critical condition, according to Nashville Fire spokesman Joseph Pleasant.

The incident is under investigation by multiple agencies, both local and federal, including the FBI and the ATF, Aaron said. Police and Tennessee Highway Patrol are conducting a shutdown of the area for the investigation. Access from the interstate through the immediate area will be restricted, he said.

Eyewitness Buck McCoy told CNN the explosion took place right in front of his home, causing his windows to be blown in.

“Everything on the street was fire,” he said. “There were three cars that were fully engulfed.”

Police previously tweeted the explosion took place outside 166 2nd Avenue N. downtown. Earlier, Nashville Mayor John Cooper told CNN he was “aware of an explosion” and was on the way to the scene.

“I do know emergency services are calling in our help, all our specialties, to investigate the cause of the explosion and I'm sure more information will be posted soon,” Cooper said.

The mayor added the explosion happened on 2nd Avenue on the edge of the Tennessee city's hospitality and tourist district in an old, historic part of town.

Footage from CNN affiliate WTVF showed smoke rising from a fire on the street, with debris littering the area.

McCoy told CNN that when he looked outside trees had fallen and broken glass was everywhere. He saw people filing out of their apartments with their animals. Firefighters told him to get as far away from the area as possible, he said.

“There's just nothing left on Second Avenue,” he said.

CNN's Paul P. Murphy and Devon Sayers contributed to this report.