The blast occurred on the morning of Feb. 15 as the Los Angeles Fire Department was on the scene of a fire on the truck near the intersection of Alameda Street and Henry Ford Avenue.
Twelve firefighters "responded to a truck with pressurized cylinders on fire," the agency said in a statement. The blast happened six minutes after they arrived.
Several firefighters were immediately rushed to Harbor-UCLA Medical Center and others were initially evaluated at the scene before they too were hospitalized.
Medical crews at Harbor-UCLA Medical Center raced to intubate Firefighter Dan Goen, who suffered the most severe injuries. He was ultimately transferred to the LA General Regional Burn Center for more specialized care.
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On Monday, Goen walked out of the facility to applause from fellow firefighters. He offered his thanks for all the support he's received and said he is looking forward to spending time with his wife and daughters.
Authorities said the truck was powered by compressed natural gas and one of its two 100-gallon fuel tanks blew up.
Of the others who were injured, four suffered moderate injuries and three had minor injuries, said Dr. Molly Deane, a trauma surgeon.
"Frankly, it's remarkable that none of them are more severely injured after watching the footage," Deane said.
The driver of the truck escaped injury after noticing something was awry with the big rig's tractor and stepped away to call 911, officials said.
The Associated Press contributed to this report.