TULSA, Oklahoma - Firefighters are working to figure out what started a fire inside a closed up Tulsa restaurant early Tuesday.

Acting District Chief Terry Sivadon says they got the call just before 12:50 a.m. to the building located near 68th and Memorial Drive.

He said a police officer first spotted smoke around the building and called the fire department.  

TFD says they're still investigating the cause, but they believe someone was trying to keep warm and started a fire near the building.

Sivadon says Macaroni Grill closed four to five years ago due to structural problems in the roof, and those same problems created issues as firefighters tried to put out the fire early Tuesday.

He says the building is now a total loss and will most likely have to be torn down.