(CNN) A Northeastern University staff member was injured Tuesday when a package he was opening detonated on the Boston campus, officials said,
"The staff member sustained minor injuries and is being treated," Shannon Nargi, a spokesperson for Northeastern University, told CNN in an email. The package was delivered to Holmes Hall, Nargi said.
The staffer, a 45-year-old man, suffered hand injuries, Boston Police Superintendent Felipe Colon said during a news conference Tuesday night.
Investigators haven't said how the package arrived at the campus and stressed the investigation is ongoing.
During the news conference, officials said they were investigating a motive.
Several federal law enforcement sources told CNN the package contained a rambling note that criticized Facebook founder Mark Zuckerberg and the relationship between academic institutions and the developers of virtual reality. CNN has reached out to Facebook for comment.
The note was in a hard plastic container and detonated when the victim opened the latches and lifted the lid, the sources said.
The package was delivered to the university's virtual reality center and was opened by someone who works in the center, the sources said.
While the employee who opened the package was not seriously hurt, the explosion caused lacerations to his hands and other injuries, the sources added.
Police were called to the scene around 7:18 p.m., Colon said. A Northeastern University police officer responded within a minute of the initial call, said Michael Davis, chief of the university police department.
"It's very important to note, our campus is secure," Davis said.
Boston Police's bomb squad and Boston Emergency Services were at the scene investigating, and the building was evacuated, Nargi said.
Boston Mayor Michelle Wu praised law enforcement's response to the incident.
"We want to make sure to emphasize that this is of the utmost priority, the safety and well-being of all our young people here," Wu said during the news conference.
The FBI Boston Division coordinated with the Boston Police Department, spokesperson Kristen Setera told CNN.
FBI Boston offered the full resources of the Joint Terrorism Task Force, its evidence response team and special agent bomb technicians to assist in the investigation, according to Jason Cromartie, assistant special agent in charge.
Just before 10 p.m., university police tweeted that the "scene at Homes Hall is currently contained."
Holmes Hall is the hub of the school's "Writing Center activities," according to Northeastern's website. University police tweeted that emergency services were responding to an incident there and asked people to avoid the area.
"We will update members of the Northeastern community when more information is available," Nargi said.