Traces of arsenic were found in the blood of freed hostage Frank Reed when he arrived last month in the United States, hospital officials and relatives said yesterday.

The Malcolm Grow Medical Center at Andrews Air Force Base -- where Reed, 57, has been undergoing medical treatment -- announced late Friday the presence of the poison, which no longer threatens Reed. The hospital said tests that screen for heavy metals such as arsenic, lead and mercury are standard for returning hostages or prisoners of war.

"These tests were performed upon Mr. Frank Reed's arrival here. The initial test for arsenic was positive. Subsequent tests confirm this exposure to arsenic and its elimination to a non-toxic level," according to a statement from Andrews. State Department officials could not be reached for comment.

Fahima Dalati, Reed's Syrian-born wife, said her husband did not know how he was exposed to arsenic during his 44 months in captivity. In a telephone interview from her home in Malden, Mass., Dalati said Reed also did not know whether fellow hostages Terry Anderson, the Middle East bureau chief of Associated Press, and Thomas Sutherland, American University of Beirut agronomist, had been exposed to it.

Hospital officials were not available for comment on how the poison had affected Reed's health or how high the level of toxins was when he was first tested.

Victims can ingest arsenic from water and food, especially seafood. Middle East pesticide sprays often contain arsenic, according to persons familiar with Beirut. Specialists said there is no way to determine if Reed's diet and environment were the source of his poisoning.

Doctors not affiliated with Malcolm Grow said arsenic can kill in large enough doses.

Peggy Say, Anderson's sister, said in an interview from her home in Cadiz, Ky., that she was "appalled and horrified" at the reported health condition of both her brother and Sutherland, who entered his fifth year in captivity yesterday.

"I was told by French hostages who came out two years ago that Terry was urinating blood. Now Frank has reported the same thing, though I was told he took medications. I am seriously concerned now. If arsenic poisoning was deliberate, it is an abomination. We need an independent doctor, maybe from the Red Cross," she said.

Carmella La Spada, chairman of No Greater Love, a nonprofit organization concerned with the care of hostages and their families, said none of the hostages freed before Reed -- including Robert Polhill, who was released in April -- was known to have poisons in their systems.

Arsenic, a silvery-white element, is used to make insecticides, glass, medicines and semiconductors. Medical authorities said exposure to high levels of arsenic can produce burning pains in the throat and stomach, vomiting, diarrhea and depression.

They said prolonged exposure to the substance can lead to a rapid, feeble pulse and a complete collapse of the body's circulatory system.

La Spada said Reed had gained weight and was playing golf. Reed was kidnapped by Islamic extremists in September 1986 on his way to the Beirut Golf Club.