She said that graduate students were filling in for the accused professors and that some students felt shortchanged by not being taught by the scholars they had signed up for.

Elizabeth Southwell, 24, a Dartmouth alumna, said she had taken courses with all three of the professors while a student at Dartmouth. News of the investigation, she said, had ricocheted among alumni over Facebook and in text messages.

“I’m very, very shocked,” Ms. Southwell said. “A large group, three of them placed on leave. Three of the professors who had some of the best reputations as teachers.”

In a separate statement on Tuesday, the president of Dartmouth, Philip J. Hanlon, said the university was cooperating with the criminal investigation of the three professors, identified as Todd F. Heatherton, 56; William M. Kelley, 45; and Paul J. Whalen, 54.

Dr. Heatherton leads a center for social brain sciences and, according to the college’s website, conducts research in social behavior focusing on self-regulation, self-esteem and self-referential processing. He had been an unpaid visiting scholar at New York University since July, with no classroom duties, but his time there ended last Thursday “by mutual agreement,” according to John H. Beckman, an N.Y.U. spokesman.

“N.Y.U. was unaware of the Dartmouth investigation until quite recently,” Mr. Beckman said. “The university was given no specifics about its nature or duration.”