Ohio state police will conduct daily sweeps of schools in Springfieldafter authorities have been forced to investigate “at least 33” bomb threats that led to evacuations and temporary building closures, Ohio Gov. Mike DeWine said Monday.

“We want to make sure, as school continues this week in Springfield, that parents have confidence that the school is in fact safe,” the Republican governor said at a press conference.

Each bomb threat has been a hoax without “any validity at all,” DeWine said.