By Staff

PROVIDENCE (CBS) – Bomb threats were made at several Ivy League schools over the weekend.

Evacuations were ordered at Brown, Cornell and Columbia universities Sunday.

Those came two days after a similar threat was reported at Yale University.

Brown evacuated several buildings near the college green in Providence Sunday, but later gave the all-clear.

None of the threats were deemed credible.

Investigators have not tracked down the source of the threats yet. Staff