Firefighters said they've never battled a house fire of this magnitude.
"You have to treat them as if they're commercial buildings. Even though it's a single family residence it's a big building," Worthington Fire Dept. Chief Kevin Groody said.
The 23,429 square foot mansion located in Wolf Pen Estates on Rama Road has been under construction since 2012. The unfinished house's assessed valued is more than $3.4 million, according to Jefferson County Property Valuation Administration.
PVA records list Rama Arla as the property owner. A family member said they are thankful no one was hurt in the fire and they're devastated by the loss.
A sign on the property posted by Paul Brar of RTS indicates he's the builder. When WAVE 3 News contacted Brar, he said he couldn't say anything about the fire because his insurance company advised him not to.
A thick plume of smoke in the front lawn obstructed the view of the house as neighbors passed by Tuesday.
"It scares me. They're my neighbors and this could happen to anyone," Vivien Schaff said.
Neighbors said they've been monitoring the construction progress, but lately there hasn't been activity.
"We had noticed nobody was here. So it looked like it's been deserted for a little while," Donna Beaven said.
It took several area crews nearly three hours to extinguish the flames. Louisville Metro Arson will handle the investigation into the cause and source of the fire.