BOSTON -- A hard plastic case that an employee said exploded in the virtual reality lab of Northeastern University wasn't sent to the lab through the postal service, according to multiple sources.
Law enforcement sources say the employee told investigators that when he opened the case Tuesday evening it depressurized with the force of an explosion.
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.
The package contained 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.
The video from the player above is from a previous report.
CNN has reached out to Facebook for comment.
The 45-year-old man who opened the package suffered minor hand injuries, according to university and law enforcement officials.
The package was delivered to Holmes Hall, where the institution's virtual reality center is located, university spokesperson Shannon Nargi told CNN.
The Boston-based university was expected to fully reopen Wednesday, Northeastern said. The university serves more than 16,000 undergraduate students, according to last year's enrollment report.
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.
University police announced the scene was "contained" just before 10 p.m.
"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.