Chief Justice William H. Rehnquist has been hospitalized with a fever, according to a Supreme Court statement.

The statement said Rehnquist, 80, went to Arlington Hospital by ambulance last night with a fever. "He was admitted for observation and tests," the statement said.

Rehnquist, rumored in recent months to be resigning, is being treated for thyroid cancer.

White House spokesman Scott McClellan told reporters that President Bush did not know about Rehnquist's hospitalization before the news broke this afternoon. "We wish him a speedy recovery," he said.

Bush is searching for a candidate for the court to replace Justice Sandra Day O'Connor, who announced July 1 that she is retiring. Rehnquist has also been the focus of intense speculation in the press and legal circles, with many analysts expecting him to announce his retirement now that the court term is completed.

The statement by the court today about Rehnquist's hospitalization came after reporters noticed that he had not come to the court building on Capitol Hill and that a court police officer was taking items from his home, according to the Associated Press. The officer first took out Rehnquist's cane and a shirt and on a later trip brought out other clothing, the AP said.

Rehnquist has not released specific details about his condition, but outside medical experts have suggested based on the limited information available that he is suffering from anaplastic thyroid cancer. That form of cancer generally is fatal within a year of diagnosis, according to doctors.

The chief justice had a tracheotomy in October to help him breathe and was absent for about five months from oral arguments at the court while undergoing treatment for the cancer. But he continued to participate in court decisions and even read one of his opinions from the bench last month. He administered the oath of office to Bush during his inauguration in January.

President Richard M. Nixon named Rehnquist to the court in 1972 and Ronald Reagan appointed him chief in 1986.