LOS ANGELES – A compressed natural gas tank exploded on a big rig in Wilmington Thursday morning, injuring nine firefighters, two of whom were hospitalized in critical condition, authorities said.

The blast occurred shortly before 7 a.m. at Alameda Street and North Henry Ford Avenue.

Firefighters had responded to the scene after getting reports that cylinders believed to be compressed natural gas (CNG) were on fire.

“There are two 100-gallon tanks on that vehicle, one of which exploded while our firefighters were putting out the fire,” Capt. Erik Scott of the L.A. Fire Department said at a mid-morning news conference.

The natural gas, Scott said, was the truck’s fuel, and the tractor was not hauling a trailer at the time.

“That explosion was significant. The ball of flame was as high as telephone poles, and it did explode one of the [power] transformers nearby,” said Scott.

In a news conference just before noon, LAFD Chief Kristin Crowley said there was no longer any threat to the public.

Sky5 aerial footage showed the charred wreckage of the big rig with burned debris — including firefighting gear — scattered around the area.

Scott said the injured firefighters were quickly triaged and treated at the scene before getting transported to a local hospital.

Officials later said that a total of nine firefighters, including two in critical condition, were sent to Harbor-UCLA Medical Center in connection with the blast.

One of the critically injured firefighters was airlifted to Los Angeles General Medical Center, which operates one of the three burn center units in the area.

Of the other seven patients, four were treated for moderate injuries while three received care for minor injuries.

“I’ve taken the opportunity to meet with every single one of our nine [injured] members and look at them and their faces,” Crowley said. “It was something I’ll never forget.”

Harbor-UCLA Medical Dr. Molly Deane said she reviewed the footage of the blast Thursday morning.

“Frankly, it’s remarkable that none of them were more severely injured,” she said.

Deane added the seven non-critical firefighters were treated for burn, blast and airway inhalational injuries.

The woman driving the truck escaped unharmed prior to the explosion, officials said.

“This is a difficult day in Los Angeles,” Mayor Karen Bass said. “The 4 million people of Los Angeles stand with [LAFD].”

Crowley said a significant incident review team will be assembled to review the response to the explosion to gather “the opportunities for improvement and lessons learned.”