(CNN) — Asiana Airlines Flight 214 passenger Ye Mengyuan died of injuries she received when run over by a fire department vehicle, and she was alive when she was hit, Coroner Robert Foucrault of San Mateo County, California, said Friday.
Police previously said she might have been hit by a fire truck after she was thrown from the plane as it crash-landed on July 6 at San Francisco's airport.
Ye, 16, of China was one of three people who died from the crash and its aftermath.
San Francisco Fire Department Chief Joanne Hayes-White, attending a news conference with Foucrault, called the incident "a tragic accident" and apologized to Ye's family.
One of the department's aircraft rescue and firefighting vehicles struck the girl while she was on the ground, possibly covered with firefighting foam being sprayed on and around the burning plane, the chief said.
"I particularly want to express our condolences and apologies to the family of Ye Mengyuan in light of the coroners' findings (in) this tragic accident," the chief said.
"Obviously this is very difficult news for us. We're heartbroken. We're in the business of saving lives," she added. "There's not a lot of words to describe how badly we feel about it."
The fire department is reaching out to the family through the Chinese consulate's office.
The investigation of what happened after the crash remains with the city's police department.
Police are reconstructing the crash scene to ascertain what happened during the rescue, the chief said. She called the crash "a difficult, challenging scene."
"We believe it was one of the specialized rigs at the airport, the ARFF rigs, aircraft rescue firefighting vehicles," Hayes-White said.
San Francisco Mayor Edwin M. Lee said he was "profoundly saddened by the involvement of a responding emergency vehicle in the death of 16-year-old Ye Mengyuan."
"On behalf of the people of San Francisco, I offer my deepest condolences and regret for her tragic death, and the deaths of her close friend, Wang Linjia, and 15-year-old Liu Yipeng," the mayor said in a statement.
Ye and Wang, also 16, were part of a group of 35 teachers and students from a middle school in Jiangshan traveling to California for a summer camp program.
Wang was found dead at the scene along with Ye. Liu died days later in a San Francisco hospital.
Foucrault, the coroner, met with the three families Thursday to discuss his findings, the fire chief said.
The mayor said firefighters and first responders helped save the lives of 304 of the 307 passengers and crew aboard the flight.
The National Transportation Safety Board is investigating the crash landing, which also injured more than 180 people aboard the flight.