The University Police Department is adding more officers to upperclassman residence halls as part of a broader effort to tighten access to buildings across campus.

The force reviewed data from crime reports covering the past five years, looking at patterns to determine where and when to place officers in specific buildings, UPD Chief Kevin Hay said Wednesday. He said the officer postings are flexible and UPD will relocate officers if trends shift.

University Police Department began cracking down on who can enter residence halls earlier this semester, stationing officers near building entrances that were not previously supervised, including Ivory Tower, where hosts were required to escort their guests inside.

Incidents of piggy-backing, when an individual enters a building behind residents who unlocked the door, have been highlighted as a campus concern.

In late October, Metropolitan and University police officers arrested 34-year-old Mergen Battulga, who trailed into the West End residence hall and allegedly attacked students. Battulga is facing three D.C. Superior Court charges for assault, and other charges for unlawful entry, threats to do bodily harm and assault on a police officer.

Another man piggy-backed into City Hall in September and attempted to sexually assault a female student.

Officers will monitor the front doors of Ivory Tower, City and Amsterdam halls, home to mainly juniors and seniors, from 10 p.m. to 6 a.m., Hay said. Surveillance at Mitchell Hall and the freshman dorms Madison, Lafayette and Crawford halls will follow the same schedule.

Security guards are already posted in Thurston and Potomac halls, where students must sign guests in at a front desk.

Hay said UPD’s community service aides – who are all students – would keep an eye on certain buildings from midnight until 4 a.m. Those residence halls include seniors-only South Hall, sophomore halls including West End, Fulbright, The Dakota and Guthridge, as well as International House.

Officers will also patrol 1959 E Street, 2109 F Street, Townhouse Row, Building JJ, Schenley, Francis Scott Key, Munson and Strong halls, along with the graduate student residence halls The Aston and the Hall on Virginia Avenue.

He said three officers patrol across the Mount Vernon Campus at all times.

Students should remain alert and increase their “sense of community” by notifying UPD if they see suspicious activity, the chief said.

“As an example, if an individual in his 40s is loitering outside of a locked residence hall at 2 a.m., ask yourself why. Is he waiting to tail-gate into the building? We would love to get calls from students when they see things like this,” Hay said.