A mutilated body found in Iraq is not that of kidnapped aid worker Margaret Hassan (search), the British government said Wednesday. But the Foreign Office said it continued to believe Hassan had been murdered, although the evidence was not conclusive.

The Foreign Office said dental tests conducted in the United States showed the body of a woman of Western appearance, found in Fallujah (search) last month by U.S. Marines, was not Hassan.

The Iraq director of the aid group CARE International (search), Hassan, 59, was abducted on her way to work in Baghdad on Oct. 19. On Nov. 16, the Arab satellite station Al-Jazeera said it had received a video showing the execution of a female hostage identified as Hassan.

British officials who watched the tape said they believed the blindfolded woman shown being shot in the head by a masked gunman was Hassan.

Hassan's four brothers and sisters released a statement last month saying they "have to accept that Margaret has probably gone and at last her suffering has ended." CARE said it was in "mourning," and Hassan's Iraqi husband, Tahseen Ali Hassan, released an emotional television appeal for his wife's body to be returned.

A Foreign Office spokesman said Wednesday that officials still believe Hassan was killed, although they cannot be absolutely certain until her body is recovered.

The Irish government said it had no new information about the fate of Hassan, who had British, Irish and Iraqi nationality.

Born in Ireland and raised in England, Hassan had lived in Iraq for more than 30 years. A fierce critic both of United Nations sanctions on Iraq and the U.S.-led invasion, she worked on projects providing food, medicine and humanitarian aid to Iraqis.

Hassan was the among the most high-profile of more than 170 foreigners kidnapped in Iraq this year, and the first female hostage to be killed. More than 30 male hostages have been slain.

U.S. Marines found a mutilated body on a street in Fallujah on Nov. 14 during the U.S. assault on the city, regarded as an insurgent stronghold. The body, clothed in what appeared to be a purple velour dress, was wrapped in a blanket, with a blood-soaked black cloth nearby. U.S. officials said they believed it was that of a Western woman.

Hassan was among nine foreign women hostages abducted in Iraq this year. Eight, including two Italian aid workers and Polish-born Teresa Borcz Khalifa, have been released.