SAN MATEO — Confirming the worst-case scenario, officials said Friday that one of the victims of Asiana Flight 214 was alive when she was run over and killed by at least one firetruck that had been dispatched to rescue survivors and extinguish flames from the burning Boeing 777.

The painful revelation raises uncomfortable questions about the response to the July 6 crash and has cast a shadow over a heroic response that saved most of the 307 passengers and crew aboard the doomed plane.

“There’s not a lot of words to describe how badly we feel, how sorry we feel,” San Francisco Fire Chief Joanne Hayes-White said at a news conference with San Mateo County Coroner Robert Foucrault.

“We commit to continue to examine our response that day,” Hayes-White said. “Could we have done something different faced with the challenges we had in terms of passengers still on an aircraft that was engulfed in flames … and the need to get to those flames? We had fuel leaking. It was a very dangerous and volatile situation.”

Ye Mengyuan, the 16-year-old victim, was covered in firefighting foam when she was run over, San Francisco police said. Officials haven’t said whether first responders made an effort to dig through the foam to search for victims, or explained how her body ended up covered in foam.

San Francisco firefighters do not train with fire-retardant foam at SFO “because of the environmental impact,” fire department spokeswoman Mindy Talmadge said Friday. But when they train for possible plane crashes at other locations, San Francisco firefighters are taught that one of foam’s many uses is to smother fumes from leaking jet fuel and other chemicals so they don’t trigger a fire, Talmadge said.

Instead of focusing on breaking through fire-retardant foam to look for potential casualties, San Francisco firefighters instead are trained to maintain “a blanket of foam” — and apply more if it starts to shrink in size to reduce any fire hazards, Talmadge said.

They key is to maintain that blanket,” she said.

San Jose firefighters don’t use fire or foam for their mandatory FAA drills at Mineta San Jose International Airport but said they do train with both during annual drills at either Moffett Federal Airfield or Salt Lake City.

But the presence of foam can quickly overwhelm a mock crash site, San Jose fire Capt. Cleo Doss said.

“When we do start dropping a lot of foam in the area it’s like skiing in a whiteout condition,” Doss said. “You can’t see anything.”

Doss saw photos of the foam covering the burning Boeing 777 at SFO and said it was “chest high.”

An investigation continues to determine exactly which fire rig or rigs ran overYe. Fire officials previously said each of the five personnel operating rescue apparatus at the crash site passed drug and alcohol screenings in the ensuing investigation. Asked Friday if any firefighters face disciplinary action, Hayes-White said, “At this moment, no. I consider it a tragic accident.”

Before Ye was run over, Foucrault said, “She was alive at the time.” She died of “multiple blunt injuries that are consistent with being run over by a motor vehicle.”

An examination of internal hemorrhaging ruled out any chance the girl was already dead when the truck hit her, Foucrault said.

The San Francisco Police Department, which continues to investigate Ye’s death, said her body was discovered in tracks in the fire-retardant foam that had been left by one of the San Francisco Fire Department’s Airline Rescue and Firefighting rigs.

Ye and 16-year-old Wang Linjia were found dead after the crash. The Chinese schoolmates were ejected from the plane after the tail snapped off when it crashed into the sea wall that abuts Runway 28 Left. Both girls were seated near the rear of the aircraft.

A third fatality was reported July 12 when 15-year-old Liu Yipeng, who was found in the wreckage still strapped to her seat, died from her injuries.

San Francisco Mayor Ed Lee and Hayes-White have reached out to the Ye’s family “to not only express our condolences and apologies but to also offer, if they are willing and interested, in sitting down so we can have a face-to-face meeting.”

Asiana Airlines said in a statement that it “extends its sincere condolences to the families of all three of the decedents.”

Retired San Jose Police Capt. Phil Beltran responded to a light plane crash that killed two men, and later drilled his team at Mineta San Jose International Airport on how to respond to the possibility of a commercial jetliner crash with mass casualties.

But no amount of drilling or mock exercises can prepare first responders for the chaotic site of a mangled jetliner, burning fuel, the screams of victims and the site of body parts, said Beltran, who ran the San Jose Police Department’s airport division from 1997 to 2000 and is now the head of campus safety at Santa Clara University.

He remembered the “surreal” crash site near Lincoln High School in 1981 after a Piper Aerostar twin-engine plane landed in pieces, killing the two occupants who were the victims of a midair murder-suicide.

“There wasn’t a part bigger than a foot and there was a fire pit where the engine went in and body parts everywhere,” Beltran said “It was just two people but it was surreal. It was nothing you ever trained for.”

Hayes-White has said that she did not think that any of the first responders had ever been through a similar emergency before.

Ken Burris, the former head ï»¿of the Federal Emergency Management Agency who responded to three plane crashes, told this newspaper that no amount of training can prepare first responders for the unique situations they will face in an actual crash of a commercial airliner.

“The difference is night and day,” he said. “We try to simulate a live environment but it can’t meet the real expectations of a very chaotic situation where there’s a lot going on. It’s all about trying to save the greatest amount of life in the shortest period of time.”

Staff writers Robert Salonga and Mark Emmons contributed to this report. Contact Dan Nakaso at 408-271-3648. Follow him at Twitter.com/dannakaso.