Family members of a Saudi inmate found dead at Guantanamo Bay prison in Cuba accused the United States on Thursday of killing their son, adding they want an autopsy in Saudi Arabia because they do not believe U.S. claims he committed suicide.

In a phone interview with The Associated Press from the ultraconservative province of Al-Qasim, the sister of Mani Shaman Turki al-Habradi al-Utaybi said she would never believe her brother had taken his own life.

"He is an extremely devout Muslim who would never, never, never commit suicide," Manyia Shaman Turki al-Habradi al-Utaybi said.

The U.S. Defense Department said al-Utaybi, Yasser Talal al-Zahrani of Saudi Arabia and Ali Abdullah Ahmed of Yemen hanged themselves in their cells early Saturday, using nooses made from sheets and clothing.

A lawyer for the families of Saudis detained in Guantanamo, Katib Fahd al-Shammary, said he also found the official cause of death difficult to believe.

"I doubt the American suicide story because of the strict security measures applied inside the detention center," al-Shammary said in a statement Thursday.

Ahmed's parents told The Associated Press Wednesday that they believe the United States killed their son, and they want his body flown home for burial.

"I respect and love the friendly American people, but they should know more what [U.S. President George W.] Bush is doing against the Muslims," Mohammed Abdullah al-Aslami said at his home in Yemen.

The deaths have brought renewed pressure on Washington to close the prison on a naval base in Cuba where about 460 men are held, almost all of them without charges. The facility has been plagued with reports of abuse and human rights violations since its opening more than four years ago.

Al-Utaybi's sister accused the U.S. of killing her brother.

"I strongly assure to you that the Americans are behind his death," she said. "We lived together for a long time, and I know that he is someone with strong faith," she added. Suicide is prohibited under Islam.

She also called for the U.S. to send his body back to Saudi Arabia for an autopsy and proper burial.

"I hope that they bring his body back [to Saudi Arabia] so I can see him for the first time in five years, and to be buried in the land of Islam," al-Utaybi said.

The U.S. military had accused al-Utaybi, 30, of being a member of a militant missionary group, Jama'at Al Tablighi. He was born in Al-Qarara, Saudi Arabia, according to a Defense Department list of Guantanamo detainees.

He had recently been recommended for transfer to custody in another country, the military said, though it was unclear if al-Utaybi was informed about the transfer recommendation before he died.

On Wednesday, the state-funded Saudi National Human Rights Group blamed U.S. authorities for the deaths of the two Saudis and cast doubt on their suicides. The Saudi government also called for the speedy release of all 134 Saudis still at the prison.

Al-Utaybi said her brother, an Islamic law student, left Saudi Arabia three years ago for Pakistan and then Afghanistan, to join "holy war."

"He left without telling us. He liked jihad and wanted to join the mujahedeen. We didn't expect him to do that," she said.

He arrived in Afghanistan three months before the Sept. 11, 2001 attacks, and was captured there after the U.S. invaded Afghanistan. But the sister said she believed her brother had nothing to do with Al Qaeda or Usama bin Laden, who is also a Saudi native.

"I believe that he was working for the Islamic relief associations," she said.

When he first arrived at Guantanamo more than four years ago, al-Utaybi sent a letter through the Red Cross to his family in Saudi Arabia, his sister said.

"He was sending his regards and telling us he is alive," she said of their last communication.