The Houston Fire Department said the incident happened at about 3 a.m. at an apartment complex on Blalock.
Crews were seen cleaning up the remnants of the fire Friday morning.
District Chief Robert Branch with HFD said a couple of people were trapped on a second-floor balcony, but firefighters were able to rescue them with no problem.
Luckily, no one was injured, though officials said one firefighter fell through the floor from the second level to the first but landed on something relatively soft and was fine.
According to HFD, the fire started in a downstairs unit and spread to three others. Two units suffered fire damage, while two had water damage.
What sparked the fire is unclear, but HFD's arson division is investigating.