MACON, Ga. — On Saturday afternoon, investigators were still on the scene of a massive warehouse fire that broke out Friday afternoon.

It happened at the ABC Supply Company, near the Middle Georgia Regional Airport, but fire investigators are still determining what caused it.

Macon-Bibb County firefighters were on scene all night after responding to the call around 5:30 p.m.

RELATED: UPDATE | ABC Supply plant fire under control, 3 firefighters treated for smoke inhalation

They are still working to get the fire completely out so they can start moving all of the melted, twisted metal from the roof out of the way.

"At this point we are trying to get an excavator out here to remove all that metal. That way we can get inside and put the hot spots out," Battalion Chief Ronnie Napier said. 

Fire investigator, Ben Gleaton, said it looked like the fire started at one end of the building and quickly spread to the other. 

Battalion Chief Ronnie Napier said they probably will not know what caused the fire until next week. 

"We're kinda babysitting it right now. We've got it under control. It's not going anywhere," Napier said.

RELATED: 'It's pretty horrific:' ABC Supply Co. branch manager watches Macon fire blaze through building

Charles Rouse, a truck driver for ABC, said he was watching the news Friday night and heard about a warehouse fire.

"15 minutes later, they came back and said 'on Delta Drive.' I said well... wait a minute. That's our place," Rouse said.

He said he could not believe what he saw when he drove up Saturday morning.

"It's hard to describe. It's like an empty spot. Just hits you in the gut," Rouse said. "I showed up out here and was like 'oh lord, it's worse,' It looks worse in person than it did on TV."

Macon-Bibb County Fire Chief Marvin Riggins told 13WMAZ at the scene, propane tanks were exploding inside the warehouse which caused the fire and smoke to grow.

Napier said the firefighters had their work cut out for them.

Four firefighters taken to Navicent last night have since been released. They were treated for smoke inhalation and heat exhaustion.

Three of those four have already been cleared to go back to work. The fourth is okay, but still has to return to Navicent for a follow-up appointment.

"They worked their tails off. They earned their paycheck yesterday. I'll put it that way," Napier said.

RELATED: U.S Coast Guard, JFRD end active search for missing firemen