Nine letters have surfaced indicating Albert Einstein had a love affair with a Russian spy during World War II. The letters, written in 1945 and 1946 by Einstein, the physicist who formulated the theory of relativity, were to Margarita Konenkova. According to a book by a former Soviet spy master, Konenkova was a Russian agent whose mission was to introduce Einstein to the Soviet vice consul in New York.

The letters were consigned to Sotheby's auction house by a member of Konenkova's family. Although the two met around 1935, it is unclear when the affair began -- whether it was before or after the death of Einstein's second wife, Elsa, in 1936.

There is no indication in the letters that Einstein was aware that Konenkova, who died in 1982, may have been a spy.

Paul Needham, a consultant to Sotheby's who translated the letters, said he made that connection himself in researching supplementary materials and coming across Konenkova's name in "Special Tasks," the memoirs of the Soviet spy master, Pavel Sudoplatov and his son, Anatoly, published in 1995.

The job of Konenkova, the book says, was "to influence Oppenheimer and other prominent American scientists whom she frequently met in Princeton (University)." But Needham and Cold War scholars said it seemed highly unlikely that Einstein would have helped the Russians in building their own bomb, given Einstein's lack of direct involvement in the United States' bomb project.