NASHVILLE (AP) — Officials are investigating why a large fireworks show in Tennessee started while some police officers were still in the blast zone.

The Nashville Fire Department said in a statement that it is working with Metro Nashville Police to determine how the "Let Freedom Sing!" fireworks show began before officers were able to leave the area and how to prevent a similar occurrence in the future.

"The safety of all personnel and the safety of the public is our department's number one priority," the statement said.

Some officers were sent to clear a building before the fireworks began, Metro Nashville Police spokesman Don Aaron told WTVF-TV. Officers were still there when someone exited and told fire officials the facility was empty, Aaron said.

"Without going through command and without checking with MNPD to ensure our personnel were out of the building, the message was relayed to start the fireworks show," Aaron said in a statement.

Officers sheltered in the building until the show was over, he said.

The free July 4 celebration featured music by Brad Paisley before the fireworks began and it drew a record 350,000 people to downtown, news outlets reported citing a statement from the Nashville Convention & Visitors Corp.