UPDATE: Fire investigators are looking into what started a fire at a former school in East Brainerd.

It's been three years since students last walked the halls in the now vacant building. Yet, this morning, firefighters were called to the school after a fire was reported.

Battalion Chief David Thompson Jr. said when they arrived, they couldn't see anything from the front of the building.

"Our dispatchers said PD is around back, and they do have fire in one of the back rooms," Thompson said.

A small fire started in a classroom, and firefighters forced their way into a door to put the flames out.

"The initial company got on scene, pulled a hose line through one of the windows and attacked a small fire in that one room," he explained.

Inside, officials found evidence that someone might've been living there when they pulled out a mattress.

Overgrown brush and trash surround the building, but a sign out front lets people know retail space is coming soon.

"Restaurants, you know, those kinds of things would be people that we would like to bring in, and there's some other larger tenants that aren't out there that we'd like to persuade to come in," Clint Wolford with Wolford Development said.

However, it's been about two years since the space was re-zoned for retail space. Channel 3 reached out to the property owner to ask about the progress, but our request was not immediately returned.

In 2016, he told us he had big plans for the nine-acre piece of property and touted new jobs. Wolford Development said the piece of property could include a grocery store and said the redevelopment plans could potentially bring in hundreds of thousands of dollars in sales and property taxes.

"This is probably the last sizable piece of property that is out there in that Hamilton Place area to develop," Wolford said.

For now, the property sits undeveloped. Investigators don't know if people have been living in the facility for a while but say it will be up to the property owners to secure the building in the future.

"Nobody was found inside, we've contacted the fire investigator, they came out and did their investigation," Thompson said.

The developer purchased this property for about $4,000,000. Monday's fire caused about $10,000 in damage.

PREVIOUS STORY: A fire early Monday morning damaged a classroom at the former East Brainerd Elementary School.

The Chattanooga Fire Department was called to the building around 3:30 a.m. The first crews on scene reported nothing was showing from the front of the building -- a Chattanooga Police officer found a small fire toward the back of the building. Firefighters broke the window to get their fire hoses inside.

Firefighters tell Channel 3 EPB had power going to the building however not all of the building had electricity.

The former school was sold by the county in 2016 to a developer with plans of building a shopping center.

A mattress was pulled from inside the classroom where it appears someone may have been staying. WRCB's crew on the scene called the fire department after hearing loud pops inside the building. A firefighter said nothing reignited.

The cause of the fire is under investigation.