BISMARCK, N.D. — Authorities say bomb threats made against a North Dakota high school might have originated overseas.

Four threats made Monday and Tuesday forced multiple evacuations at Legacy High School in Bismarck. Police Chief Dan Donlin says suspects demanded an undisclosed amount of money during at least two calls. Two other calls appear to be copycats.

Numerous computer-generated robocall threats have been reported at schools around the U.S. and in other countries in recent years, some tied to overseas accounts.

Police spokesman Mark Buschena (boo-SHEE’-nuh) said Thursday that the calls to Legacy were made by an actual person. But whether the person was overseas or using an overseas account is still being investigated.

The FBI, which is helping to investigate, declined comment, citing the ongoing investigation.