Multiple unfounded bomb threats were made over the weekend at Ivy League campuses, university and law enforcement officials said.

Cornell, Columbia and Brown universities had alerted students to threats on Sunday and deemed campuses safe a few hours later. Evacuations were ordered in some buildings on the campuses. Students were told to avoid campus until local police investigations concluded.

Two days earlier, a bomb threat at Yale forced the evacuation of several buildings as well as nearby businesses in New Haven, Connecticut. The university resumed normal operations on Friday evening.