SAN JOSE, Calif. - U.S. military investigators looking into the friendly fire death of former professional football star Pat Tillman found no criminal negligence but are recommending that nine officers, including a three-star general, be held accountable for missteps in the aftermath of the his shooting, government officials told The Associated Press.

The findings, due to be released later Monday, end twin inquiries into whether criminal acts were committed by the soldiers who opened fire on Tillman in Afghanistan, and whether the government covered up the circumstances of the army ranger's death.

Among other things, Gen. Peter Pace, chairman of the Joint Chiefs of Staff, said previously that investigators would determine whether any of Tillman's fellow soldiers were "firing a weapon when they should not have been.''

A government official who was briefed on the findings of that investigation said Monday that acting Defense Department Insp.-Gen. Thomas Gimble found no instance of criminal negligence. The official spoke on condition of anonymity because the Pentagon had not yet publicly released its findings.

The other inquiry looked at everything that happened after Tillman's April 2004 death. Senior defence officials told The Associated Press, also on condition of anonymity, that investigators would recommend that nine officers, including up to four generals, be held accountable for their missteps,

Retired Lt.-Gen. Philip Kensinger, commander of Army Special Operations, and Brig.-Gen. James Nixon, Tillman's regimental commander at the time of the shooting, are among the four generals, according to one defence official.

According to the officials, the report does not specify what should be done to the officers.

Those involved in a cover-up could have faced obstruction of justice charges, making false statements, influencing a witness or other fraudulent behaviour.

Tillman died in Afghanistan's Paktia province, along the Pakistan border, after his platoon was ordered to split into two groups and one of the units began firing. Tillman and an Afghan with him were killed. A specialist at the time of his death, he was posthumously promoted to corporal.

His death drew worldwide attention in part because he had turned down a multimillion-dollar contract to play defensive back for the Arizona Cardinals in order to join the army rangers after the Sept. 11, 2001, attacks.

Dozens of soldiers -- those immediately around Tillman at the scene of the shooting, his immediate superiors and high-ranking officers at a command post nearby -- knew within minutes or hours that his death was fratricide.

Even so, the army persisted in telling Tillman's family he was killed in a conventional ambush. It was five weeks before his family was told the truth, a delay the army has blamed on procedural mistakes.

It was not immediately clear how far up the chain of command the investigation went.

The army's Criminal Investigation Command -- the Pentagon's version of the FBI -- visited the scene of Tillman's death nearly two years after his fellow Rangers opened up on him in a barren, mountainous expanse.

They combed the landscape with surviving witnesses, found a rock stained with Tillman's blood, and re-enacted the scene where Tillman's fellow rangers swept through the canyon in their Humvee, firing up at him. Over the months, CID agents also interviewed dozens of participants and others with knowledge of the case.