Authorities in Boston are investigating the motive behind a package sent to Northeastern University that exploded when a staff member opened it Tuesday night, officials said.   

  The 45-year-old man who opened the package suffered minor injuries to his hand, according to university and police officials.   

  Investigators have not said how the package arrived on campus, stressing that the investigation is ongoing.   

  The package contained a strange note criticizing Facebook founder Mark Zuckerberg and the relationship between academic institutions and virtual reality developers, several federal law enforcement sources told CNN.   

  The package was sent to the university’s virtual reality center and was opened by someone who works there, the sources said.   

  CNN has reached out to Facebook for comment.   

  The note was in a hard plastic container and it detonated when the victim opened the latches and lifted the lid, the sources said.   

  Although the employee was not seriously injured, the blast caused hand injuries, including lacerations, the sources added.   

  Shannon Nargi, a spokeswoman for the university, told CNN the package was delivered to Holmes Hall, where the institution’s virtual reality center is located.   

  The situation unfolded around 7:18 p.m.  when police were called to the scene, Boston Police Superintendent Felipe Colon said during a news conference Tuesday night.   

  About a minute after the initial call, a Northeastern University police officer arrived at Homes Hall, said Michael Davis, chief of the university’s police department.   

  University police said the scene was “contained” just before 10 p.m   

  “It is very important to note that our campus is safe,” Davis said during the news conference.   

  Boston Mayor Michelle Wu praised law enforcement’s response to the incident.   

  “We want to make sure to emphasize that this is of the highest priority, the safety and well-being of all of our young people here,” Wu said during the news conference.   

  The FBI’s Boston division coordinated with the Boston Police Department, spokeswoman Kristen Cetera told CNN.   

  The Boston FBI offered the full resources of the Joint Terrorism Task Force, evidence response team and special agent bomb technicians to assist in the investigation, according to Jason Cromartie, assistant special agent.   

  The university serves more than 16,000 undergraduate students, according to last year’s enrollment report.   

  The campus is expected to fully reopen Wednesday, the university said.