WASHINGTON » Fifty-five colleges and universities — big and small, public and private — are being investigated over their handling of sexual abuse complaints under Title IX, the Education Department revealed Thursday.

The Education Department’s decision to release the list is unprecedented and comes as the Obama administration seeks to shed greater transparency on the issue of sexual assault in higher education and how it is being handled.

Going forward, the department said, it will keep an updated list of schools facing such an investigation and make it available upon request.

The schools range from big public universities like Ohio State University, the University of Michigan in Ann Arbor and Arizona State University to private schools like Knox College in Illinois, Swarthmore College in Pennsylvania and Catholic University of America in the District of Columbia. Ivy League schools like Harvard, Princeton and Dartmouth are also on the list.

The agency previously would confirm such an investigation when asked, but students and others were often unaware of them.

"We hope this increased transparency will spur community dialogue about this important issue," Catherine E. Lhamon, the department’s assistant secretary for civil rights, said in a statement.

Lhamon said a school’s appearance on the list does not mean that it has violated the law but that an investigation is ongoing.

Some investigations were prompted by complaints directly to the department; others were initiated by the department following compliance reviews triggered by other factors, such as news stories. That was the case at Dartmouth, where investigators visited the Hanover, New Hampshire, campus in late January to speak with students, faculty and alumni.

"We are hopeful at the end of this there will be a resolution that will strengthen our internal processes and result in a safer community," Dartmouth spokesman Justin Anderson said Thursday. "There’s always something we can learn and ways to get better."

Education Secretary Arne Duncan said there had been "lots of internal debate" about whether to release the list but that he believes in transparency; he said the more the country is talking about the problem of sexual assault, the better. Duncan said there is "absolutely zero presumption" of guilt in his mind for schools being investigated.

"No one probably loves to have their name on that list," Duncan said during a White House media briefing. "But we’ll investigate; we’ll go where the facts are. And where they have done everything perfectly, we’ll be very loud and clear that they’ve done everything perfectly."

Duncan said while being on the list might feel difficult for schools, it pales in comparison to the difficulty and trauma borne by sexual assault victims on American college campuses.

"In terms of what’s morally right there, the moral compass, whatever we can do to have fewer young women and young men having to go through these types of horrific incidents, we want to do that," Duncan said.

Title IX prohibits gender discrimination at schools that receive federal funds. It is the same law that guarantees girls equal access to sports, but it also regulates institutions’ handling of sexual violence and increasingly is being used by victims who say their schools failed to protect them.

Ada Meloy, general counsel for the American Council on Education, a higher education group, said most of the schools were probably aware there was such an investigation. "I think that every college and university in the current environment is concerned about the need to be very attentive to what they are doing with regard to policies and procedures" related to sexual assault on campuses, Meloy said.

Citing research, the White House has said that 1 in 5 female college students is assaulted. President Barack Obama appointed a task force comprised of his Cabinet members to review the issue after hearing complaints about the poor treatment of campus rape victims and the hidden nature of such crimes.

The task force announced the creation of a website, notalone.gov, offering resources for victims and information about past enforcement actions on campuses. The task force also made a wide range of recommendations to schools, such as identifying confidential victims’ advocates and conducting surveys to better gauge the frequency of sexual assault on campuses.

The department publicized guidance on Title IX’s sexual assault provisions in 2011, and complaints by students have since increased. Complaints, however, don’t always lead to an investigation.

The department can withhold federal funding from a school that doesn’t comply with the law, but it so far has not used that power and instead has negotiated voluntary resolutions for violators.

Sens. Kirsten Gillibrand, D-N.Y., and Claire McCaskill, D-Mo., have said non-compliance under the law is "far too common." They say a lack of federal resources is partly to blame for that, and they’ve sought more money to ensure timely and proper investigations.

Another law that campus sexual assault cases fall under is the Clery Act, which requires colleges and universities to report crime statistics on or near their campuses. It also requires schools to develop prevention policies and ensure victims their basic rights. Investigations under this law are not included in the list that was released.

Associated Press writer Holly Ramer in Concord, New Hampshire, and Josh Lederman in Washington contributed to this report.