TULSA, OK -- For the third time in past eight days, Tulsa firefighters responded to a fire at the Tulsa Club building Thursday morning.

The latest fire was reported at 12:39 a.m. Thursday at the building at 115 East 5th Street.

Tulsa Fire was called over reports of smoke coming out of the building's fourth and fifth floor windows.

When firefighters arrived on scene, flames were seen at a 4th floor window.

Tulsa Fire investigators have determined the fire was incendiary in nature and several persons of interest were interviewed at the scene.

"We don't know. It's undetermined at this time. We do know that it was set. We just don't know how, who set it, or why they set it," said Tulsa Fire marshal Ray Driskell.

Fire marshals were given permission to go into the building Thursday morning to look for code violations such as an unsecured building. 

The first fire at the building was Wednesday, April 14th.

The second fire happened Tuesday morning.

The vacant building is for sale but the building's broker says he believes people are gaining access to the building from the parking garage and a fire escape.