(CNN) -- The wife of a Saudi Arabian political science professor and outspoken human rights advocate said that she visited her husband in jail Saturday and that he is "in a terrible state."
Matrook al-Faleh, shown in 2004, was seized after he criticized prison conditions, says Human Rights Watch.
Matrook al-Faleh has launched a hunger strike in an effort to get authorities to tell him why he is detained, said his wife, Jamila al-Uqla.
"Prison guards took me to a room and then brought my husband to see me," al-Uqla said. "He's ill; he hasn't eaten or brushed his hair or teeth since he was detained.
"He's lost over 10 kilos (22 pounds) since the last time I saw him. He's very upset as well. He's diabetic, and his blood pressure is very high right now. He's in a terrible state."
Al-Faleh was seized at King Saud University in Riyadh on Monday, al-Uqla said.
Human Rights Watch, which issued a report condemning the arrest and urging al-Faleh's release, said his detention came two days after he publicly criticized conditions in a prison where two other Saudi human rights activists are serving jail terms.
Al-Uqla said she went to al-Ulaisa prison, accompanied by her mother, to see her husband. Prison officials were cooperative but told her he was not there and had been taken to Al-Hayer Prison outside Riyadh, she said.
"I didn't know where that prison was located, so one of their cars led the way, and we followed behind until we reached the prison," she said.
She said al-Faleh has told his interrogators -- members of the Saudi secret police -- and guards that he will not eat until he's told why he is imprisoned.
"My husband told me that they keep offering him food and he keeps refusing and that they have been threatening to force-feed him if he doesn't start cooperating," al-Uqla said.
She said al-Faleh told her he was at the university about 4 p.m. Monday when 15 members of the Saudi secret police began banging on his office door. They also called his cell phone to see whether they could hear it ring from inside, proving that he was there, she said.
After entering, the police seized al-Faleh's computer, all his computer equipment and his cell phone, she said.
Shortly after his arrest, al-Faleh said, investigators came to his holding cell to interrogate him.
"My husband refused because he said that, legally, an interrogation cannot be carried out in Saudi Arabia without the presence of a lawyer and without knowledge of what the charges are against him," she said.
He also refused a second interrogation, but after he refused a third time, his hands and feet were shackled, and he was transferred to Al-Hayer Prison, she said.
On Friday, al-Uqla said that she and al-Faleh, 54, are patriotic Saudis.
"My husband is transparent and doesn't hide anything. He says whatever he sees. He has loyalty to his country and the interests of his country," she said.
Joe Stork, deputy director at Human Rights Watch's Middle East division, said the arrest shows "that human rights advocacy in that country remains a risky business."
Phone calls to Saudi Arabia's Interior Ministry seeking comment were not answered.
Mufleh al-Qahtani, vice president of the National Society for Human Rights, said Saturday that his organization has written a letter to the Saudi government asking for information about al-Faleh's detention.
David Foley, spokesman for the U.S. State Department's Near Eastern Affairs bureau, said the United States is looking into the matter after seeing reports of al-Faleh's detention. The United States would be concerned by any restriction on freedom of speech, he said.
Human Rights Watch said al-Faleh previously sent an e-mail to human rights activists and journalists about "visiting procedures" and "detention conditions" at Buraida General Prison, where his activist friends are being held.
He called the visiting procedures laborious and compared the visiting area to a chicken coop.
"Al-Faleh's fellow activists, the brothers Abdullah al-Hamid and Isa al-Hamid, are serving prison sentences at Buraida General Prison for expressing support for a demonstration that took place in front of Buraida's secret police prison by wives and relatives of long-term detainees held there without charge," the group said.
He said the activists described the prison's conditions as filthy and crowded, and that health care is poor, according to Human Rights Watch, which said it independently confirmed such conditions.
CNN's Mohammed Jamjoom contributed to this report.