Fire officials are working to determine what caused an old hosiery mill to catch fire in Hickory early Friday morning.

Just before 7 a.m., the Hickory Fire Department responded to a structure fire on 1st Avenue SE.

Fire crews told Channel 9 that they battled the fire for more than two hours.

Investigators said the building had been vacant for years and did not have power running to it.

ALSO READ: Crews battle house fire in east Charlotte

A business owner nearby said he spotted the fire on his way to work and called for help.

“I was smelling smoke. I looked over, and smoke was pouring out of the building. ‘Where was it coming out?’ The top, so I called 911. I hope nobody was hurt,” said witness Johnny Kale.

Drone footage revealed that much of the roof of the building had collapsed, according to firefighters.

VIDEO: Crews battle house fire in east Charlotte