A former Iraqi official suspected of killing thousands of Shia Muslims after the 1991 Gulf War has mistakenly been released by American forces.
The mass grave at al-Mahawil contained bodies of missing Shiites
The US army admitted detaining Mohammed Jawad al-Neifus near the town of al-Mahawil, south of Baghdad, before releasing him when military checks uncovered nothing unusual.
Mr Neifus is suspected of involvement in a mass grave, containing as many as 15,000 bodies, discovered in al-Mahawil last month.
Human Rights Watch, which has just released a report into al-Mahawil, said the news of his release would anger locals already suspicious of US pledges to bring perpetrators to justice.
The US army has said it is investigating the error and has offered a $25,000 reward for Mr Neifus' recapture.
With one of the chief suspects gone, we may never know what happened [at al-Mahawil]
Human Rights Watch
He was released from the Bucca internment facility in Umm Qasr on 18 May, US Central Command said in a statement.
He was captured on 26 April in the city of Hilla, not far from al-Mahawil, and turned over to the Army Military Police three days later.
Central Command said he was screened by military lawyers - a regular procedure for all detainees - who found nothing unusual about his story and cleared him for release.
"US military forces are solely responsible for his erroneous
release and are conducting a thorough investigation to ensure no further recurrences," the statement said.
"Coalition forces will use all means available to bring Neifus
to swift justice and are offering a $25,000 reward for
information leading to his capture."
Mr Neifus is suspected of being involved in the murder of
thousands of Shias when former President Saddam
Hussein cracked down on a Shia rebellion in the south of the country as Iraqi forces retreated from Kuwait in 1991.
MASS GRAVES IN IRAQ
Kirkuk: Kurdish officials report discovery of 2,000 bodies
Muhammad Sakran: Reports say more than 1,000 bodies found
Babylon: Children's bones reportedly among remains found
al-Mahawil: Up to 15,000 bodies feared buried
Najaf: 72 bodies found
Basra: Grave believed to contain about 150 Shia Muslims
Abul Khasib: 40 bodies reportedly found
Relatives of those who died have told New York-based Human Rights Watch that their loved ones "disappeared" after they were apprehended by Iraqi security troops at roadblocks or in house-to-house searches.
The organisation's senior researcher, Sam Zia-Zarife, told BBC News Online that Mr Neifus was a prime suspect in the crimes at al-Mahawil and was seen as crucial to uncovering the truth of what happened.
"The destruction of evidence at the site has already made it quite problematic to conduct a reasonable accountability. Now, with one of the chief suspects gone, we may never know what happened," he said.
"It will go down extremely poorly with people around al-Mahawil. This will surely fan the conspiracy theories among those who believe the US is not serious about bringing people to justice in Iraq."