Los Angeles fire trucks are seen at the scene of an explosion on February 15, 2024.
CNN  — 

At least nine Los Angeles city firefighters have been injured in a semi-truck explosion and two are in critical condition, fire officials said Thursday.

The semi-truck was fueled by compressed natural gas and one of the two 100-gallon tanks aboard exploded as firefighters attempted to put out a fire, Los Angeles Fire Capt. Erik Scott said.

The clean-air semi-truck is still an active fire situation, but there is no longer any threat to the community, according to Fire Chief Kristin Crowley.

A ball of flames reached as high as the top of nearby utility poles burst. “It actually did explode one of the transformers nearby,” Scott said of the ball of flames.

Of the nine victims initially taken to Harbor UCLA Medical Center for treatment, two are in critical condition, and the other seven are being treated for moderate to minor injuries. One of those with critical injuries has since been airlifted to another hospital for further treatment, fire officials said.

Trauma surgeon Dr. Molly Deane said the firefighters were initially evaluated for burn, blast and airway inhalation injuries.

“Frankly, it’s remarkable that none of them are more severely injured,” she said after seeing video of the fireball.

Some firefighters were believed to have been on top of a truck and were blown back with the force of the explosion.

“That tells us there’s now maybe multiple mechanisms of injury at play which can then lead to multiple types of injury,” Deane explained.

“I’m reminded of how heroic our members are and each and every day they are putting themselves in harm’s way to provide an incredible level of expertise and professionalism for the people we serve,” said Crowley.

Hazardous material specialists on the scene are monitoring the air in the area and report normal levels at this time. Waves of firefighters will be coming in to fully extinguish the fire that remains as the gas dissipates into the air, Scott explained.

Aerial footage from the scene shows charred firefighter gear and clothing littered on the street near the wreckage of a nearly unrecognizable chassis of a semi-truck. A few cars parked nearby have shattered windows, likely a casualty of the explosion.

The truck driver was unhurt in the incident and she remains on scene and is cooperating with investigators, said Scott.

The explosion happened in an industrial part of Wilmington, near the Port of Los Angeles, just west of Long Beach.

This is a developing story and will be updated.