This photo, courtesy of Harvard Law student Elizabeth Tuttle, shows portraits of Harvard Law School professors, with a black piece of tape covering the face of a black professor. (Elizabeth Tuttle)

Portraits of Harvard Law School professors line the walls of Wasserstein Hall. But on Thursday morning, black tape covered the faces of African American professors’ images, prompting campus police to investigate the act as a hate crime, Harvard Law dean Martha Minow said in a statement.

“Expressions of hatred are abhorrent, whether they be directed at race, sex, sexual preference, gender identity, religion or any other targets of bigotry,” Minow said.

At a campus community meeting Thursday, Minow acknowledged that racism is a “serious problem” at the law school and said that “racism exists in America and in the United States and in Harvard and in Harvard Law School,” reported the Harvard Crimson, a campus newspaper.

prof A Harvard Law School professor’s portrait was defaced on Nov. 19, 2015. (Elizabeth Tuttle)

Student activists have called the incident “hateful retaliation” against black student activism. The portraits were defaced at a time when conversations about institutional racism on campuses have been thrust into the national spotlight. Earlier this month, the University of Missouri president resigned amid growing complaints, protests and boycotts over his handling of racism and bigotry on the system’s flagship campus.

At Harvard, students have organized an effort to change the law school’s crest, which is the same as the coat-of-arms of slaveholder Isaac Royall Jr., whose estate help found the school. The Royall Must Fall group describes itself as “a movement of students calling for the decolonization of our campus, the symbols, the curriculum and the history of Harvard Law School.”

[Why some students say Harvard Law School’s crest is ‘a source of shame’]

Harvard students circulated photos of the defaced portraits soon after the discovery. Second-year student Michele Hall told The Washington Post that while she was upset upon seeing the images, “I also wasn’t surprised. This is part and parcel of what is happening here at Harvard and also at other institutions across the country.”

Hall, who wrote about the law school incident on Blavity, called the defacing of the portraits “an act of bias and an act of hate meaning to show that we don’t belong, that black professors don’t belong here,” she said. “It’s part of a larger narrative of black students and students of color not belonging here and being excluded here.”

Minow, the dean, said in an e-mail to the law school student body that she was “saddened and angered by this act,” the Boston Globe reported. The campus community meeting, already scheduled for Thursday, ended up centered on the incident and racism, Hall said.

prof3 One of the Harvard Law School professors’ portraits that was defaced on Thursday. (Elizabeth Tuttle)

“Here at [Harvard Law School], we are focused on efforts to improve our community, examining structures that may contribute to negative experiences of any members of our community, and pursuing opportunities where the School can both change and support change,” Minow said in a statement.

The incident also happened a day after students from Harvard and nearby schools joined in demonstrations to show support for black activists on campuses nationwide. Third-year law student Jonathan Wall told the Globe he was “disgusted” by the defacing, and said “it seems to be in response to yesterday’s day of activism.”

[Increasingly unified protests over race gain voice nationally with #studentblackout day]

Harvard campus police did not immediately respond to The Post’s inquiries. A spokesman told the Globe there was an “open and active investigation.”

Professor Ronald Sullivan tweeted a photo of his defaced portrait. “All faculty of color woke up to the same thing this morning,” he wrote.

But as news spread of the incident, students placed their own messages alongside the portraits: Post-It notes with positive messages about those professors.

“Professor Ogletree inspired me,” read one such note. “I am proud to have been his student.”