CHICAGO (WLS) -- Several Chicago firefighters were injured while battling a large house fire in the city's Roseland neighborhood on the South Side.
Fire officials arrived at the home near 112th and Princeton just after 3:20 p.m. Saturday afternoon. Less than 10 minutes later, firefighters called for a 'mayday."
"Look at my house," said Tomorra Watts. "Look at that! You can see right through there! You see right through it!"
A warm embrace is all Watts has left. She was walking back to her home of seven years from down the street when she saw it engulfed in flames.
"All of a sudden I heard a fire truck come by," she said. "[I] noticed that they were coming to my house!"
Firefighters said there was heavy smoke on the second floor, as well as some smoke on the first floor.
Watts said she has no idea why her house would have caught fire.
"I don't have no idea. I have no kerosene, the gas is on," she said.
A neighbor captured cell phone video while at least 100 firefighters tackled the blaze before suddenly there was a loud explosion that rocked multiple homes.
"I heard a big boom and then it was a lot of smoke and then the firefighters were coming out of the house and the firefighters were saying we gotta go, we gotta go get out," said neighborhood Janeice Fletcher.
It's believed there was a flashover at the fire, blowing four firefighters off the porch, officials said.
WATCH: CFD gives update on Roseland fire
"Everything in there reached its ignition temperature, and once it got a source, it just kinda goes. Everything lights up, and it's the energy and force behind it that push," explained CFD Fire Commissioner Annette Nance-Holt.
The rare occurrence sent seven firefighters to the hospital, according to the Chicago Fire Department. Four were transported to Advocate Christ Medical Center and three were taken to Little Company of Mary Hospital.
Six of those firefighters are now out of the hospital, while another has been transferred to Loyola Medical Center to be treated for a burn, officials said.
"People don't realize. Every day, our firefighters and paramedics, they get up and go to work not knowing that day if they'll come back home. They put everything on the line to make sure we're safer," Nance-Holt added.
A resident was outside of the home when the fire department arrived, according to CFD. No one else was inside.
CFD officials tell Eyewitness news the mayday call has been secured.
Officials said there were no smoke detectors were found inside the home.
As the firefighters recover, people on the block are working together to support their neighbor.
"If you need help, we are here," said neighbor Angie Willaims. "Place is here for you."
The cause of the fire is under investigation.
Officials said they expect to have an "after-action report" within the next few days.
"Try to determine, as we talk to all the members who were there on the scene, what actually occurred so that this doesn't happen again -- if it can be avoided," Nance-Holt said.