Dunbar High School students, staff, and Second Gentleman Doug Emhoff had to evacuate the building after an apparent bomb threat on Tuesday. Emhoff visited the Ward 5 high school to participate an event celebrating Black History month, but U.S. Secret Service quickly removed him due to a security threat, NPR confirms.

DC Public Schools press secretary Enrique Gutierrez reportedly told White House press covering the event that Dunbar High School had received a bomb threat, and everyone needed to evacuate as a precaution.

Roughly 15 minutes into the event, U.S. Secret Service ushered Emhoff out of the building, according to NBC News. Students and staff were then told to evacuate over the intercom roughly an hour before class was to be dismissed for the day, according to WUSA9.

The school’s principal, Nadine Smith, told press at the scene that they followed DCPS protocol and instructed students to leave the school for the remainder of the day, which was around 2:30 p.m. Teachers stayed on the football field for another hour longer, however, as police dogs searched the building, according to the Post.

Gutierrez tells DCist/WAMU that the Metropolitan Police Department responded to the bomb threat at Dunbar High School and is continuing to investigate. “All students and visitors were safely evacuated in accordance with DC Public Schools protocols and given the time of the incident, students were then dismissed for the school day,” he says. “DC Public Schools values the safety of all students, staff, and visitors and will continue to support the Dunbar community as MPD investigates this incident.”

The communications director to the Second Gentleman, Katie Peters says via Twitter, “We are grateful to Secret Service and D.C. Police for their work.”

 At a press conference later that afternoon, MPD Executive Assistant Chief of Police Ashan Benedict announced there is no ongoing threat to Dunbar and police rendered the Truxton Circle neighborhood school safe. Police have not yet identified a suspect, but are still looking into the threatening phone call made to the school’s front desk at 2:15 p.m.

Benedict also said Tuesday’s incident at Dunbar does not appear to be related to the string of bomb threats affecting several Black universities in the region. That is based on preliminary information, he added, so the Federal Bureau of Investigation is still probing a potential connection.

According to the school’s website, Dunbar was the first public high school in D.C. and nationwide to serve Black students. Emhoff had reportedly visited to see the school’s history museum.

This post has been updated to include the police press conference. Debbie Truong contributed reporting.