Northside Elementary School bomb threat one of many across the U.S.

MIDDLETON, Wis. (WMTV)-- Multiple bomb threats were called in to schools across the country Monday morning, including one at Northside Elementary School in Middleton.

Perry Hibner, Communications Director for the Middleton-Cross Plains School District said the bomb threat was called in around 11:45 a.m. Hundreds of students had to be evacuated and taken to nearby Gateway Community Church.

Police then did a sweep of the school's interior and exterior before determining there was nothing suspicious. School was back in session at around 2:30 p.m. and will be back to normal Tuesday.

"I don't think it makes you feel better or worse," said Hibner.

"Unfortunately we live in a world where these things happen all too often, so you just need to be prepared for it."

Officials say the call was short and automated.

Many other school across the county received similar bomb threats.

Several U.S. schools said they recorded calls from an electronically disguised voice reporting a bomb, multiple police agencies told NBC News. Many said the calls came in around 2 to 2:30 p.m. ET.

The Associated Press reports this could be could be the latest example of so-called "swatting" against schools.

They report that in recent months, hoaxers playing online games have allegedly used proxy servers and other high-tech identity-disguising tools to anonymously threaten schools online or in phone messages with electronic voices to trigger a huge police response, including SWAT teams.

Schools in Green Bay, Appleton, Port Washington, Racine and Oshkosh were similarly threatened.

Other reports emerged in at least 20 other states (Colorado, Delaware, Florida, Illinois, Iowa, Maine, Massachusetts, Minnesota, Montana, New Hampshire, North Dakota, Maryland, New York, Oregon, Rhode Island, South Dakota, Utah, Vermont, Washington and Wyoming) and as far as the United Kingdom.

In Britain several schools received a 90-second recorded call from a voice with an American accent promising that "shrapnel" would "take the children's heads off," according to multiple news reports. Many of those schools reported that the calls also came in about the same time, in this case about 10 a.m. local time.

NBC News reports none of the threats were known to have been found to be credible. Some of the schools targeted decided to remain in session.

The FBI told NBC News that it was aware of the threats, adding, "We remain in touch with our law enforcement partners to provide assistance if needed."