(CBS) — Oswego schools are on high alert this week after someone hacked into an email account and sent threats against children.

Oswego police say it was a hoax but they’ve ramped up security in the schools anyway. More than 300 people in a Yahoo group set up for Southbury Elementary School parents got an email on Sunday. Police aren’t giving specifics about what it said, but do say the emails were routing out of California and the Netherlands.

Community Unit School District 308 spokesman Brian Graves says they take any threat like this seriously.

“We are doing everything to assure that the children are safe and follow procedures and protocol to ensure a safe environment,” Graves said.

Graves says there’s no timeframe for how long extra security will beefed up at the schools. He says as long as it takes to make everyone feel safe again.