Four Ivy league universities received bomb threats over the weekend that eventually were dismissed by police as “not credible.”

Columbia University, Cornell University and Brown University received bomb threats on Sunday afternoon, while Yale University received a bomb threat on Friday.

The threats caused all of the schools to order campus-wide evacuations for multiple locations and buildings. Threats made to the universities on Sunday were called about an hour apart. Each of them was dismissed as false alerts only a few hours later.

“Following an investigation, today’s bomb threats were deemed not credible by the NYPD and the campus buildings have been cleared for re-occupancy. We thank those individuals affected for their patience and cooperation in evacuating,” Columbia University wrote Sunday on Twitter.

The threats to Columbia came from a Twitter user named “Jia Nakamura,” who posted a claim that he was on campus armed with AR-15’s and Glock 10 pistols. The user wrote that if any police approached “all explosives" would be activated, according to Columbia Daily Spectator. The Twitter account is now suspended.

Cornell reported that the threat to their campus was made through an anonymous call to 911 dispatchers of bombs being placed in multiple buildings. Brown announced the bomb threat on Sunday through a "Brown Alert" text message to students.

Yale Police Department Chief Ronnell Higgins said on Sunday that it is too early to say if all the threats are connected.

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