St. Olaf College is taking the unusual step of removing the name of a once-beloved professor from a campus building because of what it calls "credible evidence" of sexual misconduct over the course of several decades.

Since 2002, the arts building has been named in honor of Reidar Dittmann, a Holocaust survivor who taught art and Norwegian at the Northfield college for more than 45 years and died in 2010 at age 88.

But on Thursday, St. Olaf President David Anderson announced that Dittmann's name will come down from the building amid revelations that multiple former students had come forward with accusations of sexual misconduct.

"This is a very difficult day at the college," Anderson said in an interview. "Frankly, every college has something like this in its history, and when you become aware of it, you have to respond to it."

Dittmann's family issued a statement that said: "We are shocked and dismayed by the turn of events that has resulted in stripping his name from the Art and Dance Center at St. Olaf College. The allegations of sexual misconduct from decades ago deeply trouble his family, many members of whom proudly attended the college and grew up with it as an integral part of our lives. We abhor sexual misconduct without exception, but we are also devastated by the impossibility of due process for the person we knew and loved."

Anderson said the allegations, some dating back decades, surfaced in the past year as a result of St. Olaf efforts to reach out to survivors of sexual assault.

When the allegations began surfacing, Anderson ordered an investigation. Carl Lehmann, the college's attorney, was able to confirm enough details through witnesses and records to support the sexual misconduct accounts, said Anderson.

He did not release details of the allegations.

"You reach a point where you have a sufficient degree of evidence that's credible and verifiable and comes from multiple sources," Anderson said. "Then you're in a tough spot. Are you going to say, well, because the alleged perpetrator is deceased, we're not going to take any steps, even though we have this very high degree of certainty of what happened? Or, knowing what we know now, we can't go forward with that name on the building."

In a campuswide letter Thursday, Anderson disclosed that "several alumni" had come forward saying they had been victims of sexual assault or misconduct by faculty or staff members in the past. He did not say how many identified Dittmann, who taught from 1947 to 1993, as the perpetrator.

"I'm the first person to say that Dittmann is a beloved figure by many," said Anderson. He founded the school's international studies program and was director of its art museum. The king of Norway awarded him the St. Olav Medal in 1977.

Born in Norway, Dittmann joined the resistance to fight the Nazis during World War II, and survived the notorious Buchenwald concentration camp, where he was a political prisoner. His story was memorialized in a short film, "Prisoner 32,232," made for the Minnesota Historical Society's Greatest Generation project.

After the war, he won a scholarship to study at St. Olaf, and joined the faculty in 1947.

His family denounced "the process used to indict our father posthumously; the haste with which the college reached its conclusion; and finally, the public humiliation our family is experiencing as a result of the college's communications of their actions."

In his campuswide letter, Anderson apologized to those who said they had been victims of Dittmann or other St. Olaf faculty or staff. "While we can't change the past," he wrote, "we can confront it and strive to make amends."

Maura Lerner • 612-673-7384