Harvard Law School has concluded the first phase of an investigation into what workers called discriminatory labor practices, including unfairly firing longtime employees and requiring those who speak Spanish to learn English.

The Law School initially launched the investigation after a delegation of custodial workers from the Law School went to Dean Martha Minow’s office almost two weeks ago and submitted a letter of complaint. Dean Minow authorized the investigation almost immediately.

The first phase of the investigation involved interviewing a large number of Law School administrators. The Law School is slated to begin a second round of interviews, though the University declined to comment on the nature of the discussions.

The alleged practices, according to the letter, began approximately six months ago, just after an unidentified administrator was hired by the Law School.

Leaders within SEIU Local 615, the union representing Harvard custodians, said they were pleased with the University’s quick response to their complaint.

“Obviously, this is very good,” Wayne M. Langley, director of higher education for Local 615, said of the University finishing the first portion of its investigation. “We’re really happy with the progress that the University is making.”

Custodians on the delegation hope this process will lead to a quick improvement in job quality.

“Hopefully, since the investigation is going so quickly, we’ll be able to work in a better place very soon,” said one member of the delegation, who wished to remain anonymous to protect his relationship with his employer.

The University declined to comment on the ongoing investigation but said it is treating the complaint as a matter of great importance.

“We take allegations of discrimination very seriously,” University spokesperson Kevin Galvin wrote in an email statement. “Representatives of the Law School and the University’s Office of Labor and Employee Relations are meeting directly with union representatives and the staff members involved in order to gather information about the complaint.”

Langley said that he appreciates the seriousness with which the University is treating the investigation. He emphasized the importance of the University and union continuing to work together to come to a solution.

“It’s very important that they are keeping us updated—they’re sticking to their word,” Langley said. “Together we can hopefully come to a solution to this issue.”

Langley said that while the complaint comes in the midst of custodial contract negotiations between Local 615 and the University, it is unlikely to influence contract discussions.

“They’ve responded appropriately and we’re very pleased with that,” Langley said. “Everything should proceed smoothly.”

—Staff writer Mercer R. Cook can be reached at mcook@college.harvard.edu.