BOSTON — The U.S. Justice Department has threatened to sue Harvard University to obtain a trove of records as part of an investigation into the school’s admissions practices following a lawsuit from a group of Asian-American students.

A Nov. 17 letter from the department gives Harvard until Dec. 1 to turn over a variety of records that Justice officials requested in September, including applications for admission and evaluations of students.

The department said Harvard has pursued a “strategy of delay” and threatened to sue if it doesn’t meet the department’s deadline.

“We sincerely hope that Harvard will quickly correct its noncompliance and return to a collaborative approach,” the letter said, adding that “Harvard has not yet produced a single document.”

The inquiry is related to a federal lawsuit filed by a group of students in 2014 alleging Harvard limits the number of Asian Americans it admits each year. A similar complaint was made to the Justice Department.

A statement from Harvard on Tuesday said it will “certainly comply with its obligations” but also needs to protect confidential records related to students and applicants.

The university said it has been “seeking to engage the Department of Justice in the best means of doing so.”

Many elite schools defend admissions approaches that consider race among other factors as a way to bring a diverse mix of perspectives to campus. Harvard has previously said its practices are legally sound.

The Supreme Court last year upheld race-conscious admissions at the University of Texas but said the ruling didn’t necessarily apply to all other schools.

Edward Blum, the legal strategist behind the 2014 lawsuit against Harvard, applauded the investigation into what he called “discriminatory admissions policies.”

“Harvard’s Asian quotas, and the overall racial balancing that follows, have been ignored by our federal agencies for too long,” Blum said in a statement Tuesday. “This investigation is a welcome development.”

The school’s early correspondence with Justice officials suggested that the department only wanted to weigh in on the lawsuit, but later letters revealed Harvard is the target of an inquiry.

A Nov. 7 letter from a Harvard attorney said it was “highly unusual” for the department to open an investigation into a complaint more than two years after it was filed and while it’s still being decided in court.

The lawyer, Seth Waxman, demanded that investigators share their case files with Harvard, prove their authority for the inquiry and guarantee confidentiality of Harvard’s records.

In the Nov. 17 response, Justice officials said steps would be taken to shield Harvard’s records from the public, but refused to share their files.

“For obvious reasons, the Department of Justice generally does not share its civil investigative case files with the targets of its investigations,” the letter said.