A truck’s fuel tank exploded early Thursday in a neighborhood south of downtown Los Angeles, sending a fireball into the air and injuring nine of the 10 firefighters responding to the blaze, including two critically, fire officials said.

All nine Los Angeles firefighters were rushed to Harbor-UCLA Medical Center and were stabilized, and one of the critical patients had to be intubated and airlifted to a burn unit at Los Angeles General Medical Center, said Dr. Molly Dean, a trauma surgeon.

Of the others who were injured, four suffered moderate injuries and three had minor injuries, Dean said.

“Frankly, it’s remarkable that none of them are more severely injured after watching the footage,” Deane said. “Most people should do fairly well.”

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 tractor was fueled by compressed natural gas carried in two 100-gallon (378-liter) tanks, one of which exploded six minutes after firefighters arrived on the scene in Wilmington. The neighborhood is 18 miles (29 kilometers) south of downtown, near the ports of Los Angeles and Long Beach.

Deane spoke outside the medical center at a news conference with the fire chief and Mayor Karen Bass, who said it was “a difficult day in Los Angeles.”

TV news helicopter video showed charred and mangled parts of the truck with a small flame still burning along with discarded firefighting gear where the injured crew members were initially treated.

“The ball of flame was as high as these telephone poles, and it actually did explode one of the transformers nearby,” fire Capt. Erik Scott said, adding that the second fuel tank was “still off-gassing, and therefore there’s a minor threat.”

The blast occurred adjacent to an industrial area separated from a neighborhood by a wide street and a rail line. No homes were in danger, Scott said, though a large perimeter was set up after the explosion, and some 160 firefighters responded.

“Today is a day, I think, where all of us can take a moment to recognize how intrinsically dangerous firefighting can be,” said fire Chief Kristin Crowley.

She said her department would review their response.

“This team is highly trained, and it will look at every single aspect of this incident and gather the opportunities for improvement and lessons learned,” she said.

(AP)