ORLANDO, Fla. — The cause of the massive Orange County apartment fire that left more than 60 people displaced -- including students who start school Monday -- may never be known, firefighters said Thursday.

The three-alarm fire destroyed 12 units at the Royal Isles Apartments on Wednesday. On Thursday afternoon, the Orlando Fire Department released preliminary findings in their investigation into what started the massive fire.

Investigators said there's no evidence the fire was suspicious or malicious in nature, and they don't think it was intentionally set or sparked by anything electrical.  

Investigators said the fire burned so hot, they might never determine what started it.  

Firefighters said one woman told them that her grandson alerted her to the fire, which was near a couch in their living room.

They said they got several 911 calls after the fire broke out, but those calls didn't come until after some residents first tried to fight the fire themselves. Firefighters urged people to always call 911 immediately at the first sign of a fire, so the fire trucks can get rolling.

Luckily, in this case, no people or pets were hurt in the fire; everyone made it out safely.

"You work your bones just to get all that stuff in there, and it just disappears in an instant. For me, that hurts," said Rafael Bruno, who lost belongings in the fire.

Alex Lespier lives just across the parking lot.

"All of a sudden, I heard a popping noise, (and) I thought it was fireworks, no big deal. But then all of a sudden... I didn't know how the flames started it," he said.

"I feel bad for the victims, because like I wish I could help them, donate to them, so I could help them," Lespier said.

Just a few days before school resumes, administrators at two area schools -- Engelwood Elementary and Jackson Middle -- were hoping to help students affected by the fire.

Of the more than 60 people displaced, 16 were students who are scheduled to start school in Orange County on Monday.

At a previously scheduled teacher meet-and-greet Thursday at nearby Engelwood Elementary, where several displaced students are enrolled, people collected donation items and money so the students could have uniforms, supplies and hygiene products when they begin the school year.

The Red Cross provided shelter for displaced families Wednesday night and was working with victims to find permanent housing.

"We'll be working with them for days to come, because for most families, they've never been through anything like this before," Red Cross Orlando Executive Director Sherri Monroe said. "Next (for them) is a big question mark, and our folks will help them work through that."

The Salvation Army also is assisting.