OKLAHOMA CITY - The Oklahoma State Bureau of Investigation (OSBI) has opened three cases into threats made against lawmakers.

Lawmakers contacted OSBI about the three threats over the last 24 hours, and a fourth case is expected to be opened soon, according to a release issued Thursday afternoon. The subjects of the threats were not disclosed.

The threats come at a tumultuous time at the state Capitol, with teachers protesting in record numbers over education funding.

This is a developing story.

Keep checking with News 9 and News9.com for more information.