The campus is now “secure and open” with beefed up security, the university said Wednesday afternoon.
The employee told investigators that when he opened the package, it depressurized with the force of an explosion, law enforcement sources said.
But Boston Police and FBI bomb technicians didn’t find any evidence of explosives nor an initiation system capable of causing an explosion, a source briefed on the investigation told CNN.
And the package wasn’t sent to the lab through the postal service, according to multiple sources.
The package did contain a rambling note that criticized Facebook founder Mark Zuckerberg and the relationship between academic institutions and the developers of virtual reality, several federal law enforcement sources told CNN.
CNN has reached out to Facebook for comment.
The 45-year-old man who opened the package suffered minor hand injuries, university and law enforcement officials said.
“Events such as the incident that took place on our Boston campus last night can create or heighten anxiety for many of us,” said a joint statement from David Madigan, Northeastern’s provost and senior vice president for academic affairs and Kenneth Henderson, chancellor and senior vice president.
“We would like to underscore what was communicated to our community last night: Multiple law enforcement agencies have determined that the campus is safe and secure.”
Northeastern is offering support services such as confidential counseling for students and staff, the university said.
A multi-agency response
Police were called to the scene around 7:18 p.m., Boston Police Superintendent Felipe Colon said 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 police department.
“It’s very important to note our campus is secure,” Davis said during the news conference.
Boston Mayor Michelle Wu praised law enforcement’s response.
“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.
The FBI Boston Division coordinated with the Boston Police Department, FBI spokesperson Kristen Setera told CNN.
The FBI offered the full resources of the Joint Terrorism Task Force, its evidence response team and special agent bomb technicians to assist in the investigation, said Jason Cromartie, assistant special agent in charge.
CNN’s Liam Reilly, Josh Campbell, Sharif Paget, Zenebou Sylla and Mark Morales contributed to this report.