The US government has confirmed that the partial remains of victims of the September 11 2001 attacks on the Twin Towers in New York and the Pentagon were incinerated by a military contractor and sent to a landfill site.
The surprise disclosure is the latest of a series of revelations about the Pentagon's main mortuary for the war dead.
It was mentioned only briefly, with little detail, in a report by an independent panel that studied underlying management flaws at Dover Air Force Base mortuary in Delaware.
A 2011 probe found "gross mismanagement" there, but until yesterday there had been no mention of Dover's role in handling remains of victims from the destruction of the World Trade Centre in New York and the attack on the Pentagon in suburban Washington.
US Air Force leaders, asked about the September 11 matter at a news conference, said they had been unaware of it until the head of the independent panel, retired Army general John Abizaid held a Pentagon news conference yesterday to explain his panel's findings.
"This is new information to me," air force secretary Michael Donley said.
He said it was unclear whether the matter would be investigated further.
Defence secretary Leon Panetta's press secretary, George Little, said Mr Panetta "never would have supported" the disposal of remains in a landfill. "He understands why families would have serious concerns about such a policy," he said.
Debra Burlingame, whose brother Charles Burlingame, pilot of the passenger plane that was flown into the Pentagon by terrorist hijackers, said she attended a ceremony at Arlington National Cemetery at which unidentified 9/11 remains were buried in an engraved coffin.
"They were treated with great respect and great ceremony," Ms Burlingame said. "The Department of Defence was exceedingly sensitive and treated those unidentified remains with great respect. ... I would want to know more."
President Barack Obama was informed of the review and supported the Pentagon's plan to address failings, "so that these types of incidents never happen again", White House press secretary Jay Carney said.
The Abizaid report primarily focused on management reforms to a "dysfunctional, isolated" Dover mortuary chain of command. It cited the September 11 matter while explaining the history of problems at Dover that came to light last year through complaints from whistleblowers who revealed the mishandling of war remains.
The practice at Dover of cremating partial remains and sending them to a landfill began shortly after September 11 2001, the report said, "when several portions of remains from the Pentagon attack and the Shanksville, Pennsylvania, crash site could not be tested or identified".
The terrorist-hijacked airliner that slammed into the west side of the Pentagon killed 184 people, and the plane that crashed in a field near Shanksville killed 40.
The Abizaid report said that in line with Dover's policy, "cremated portions were then placed in sealed containers that were provided to a biomedical waste disposal" company under air force contract. "Per the biomedical waste contract at that time, the contractor then transported these containers and incinerated them," it said.
The report said Dover authorities assumed that after incineration "nothing remained". But a Dover management "query" found that "there was some residual material following incineration, and the contractor was disposing of it in a landfill". It added that use of the landfill was not disclosed in the waste disposal contract.
"We don't think it should have happened," Gen Abizaid told reporters.
It was unclear whether families of the attack victims were aware remains had gone to contractors and then to the landfill.
In the case of September 11 victims, some remains from the Pentagon, where American Airlines Flight 77 crashed, were buried at Arlington National Cemetery on the anniversary of the attacks. Three caskets of unidentified remains from the crash of United Airlines Flight 93 in Shanksville were buried there last September.
In Pennsylvania, Somerset County coroner Wallace Miller said he was surprised that remains from Flight 93 might be involved in the new Pentagon report. "I wouldn't know how there would be any possibility how any remains would get to Dover," he said.
He said the only remains he knew of that would not be in Pennsylvania were those of four of the hijackers that were being held by the FBI for potential military tribunals.
More than 9,000 human remains recovered from the ruins of the World Trade Centre in New York City remain unidentified because they are too degraded to match victims by DNA identification. The remains are stored at the city medical examiner's office and are to be transferred to a subterranean chamber at the National September 11 Memorial & Museum, once set for opening this year but now delayed.
Diane Horning, who lost her son Matthew at the World Trade Centre, said she was shocked by the latest revelations.
"We need a protocol to be put in place so that we know this can never happen again," she said. "Not only am I broken-hearted but I am outraged."