OKLAHOMA CITY - The lock down at John Marshall High School has been lifted after authorities found no credible threat to the school.

The school was placed on a precautionary lock down after a threatening email was found on a school iPad. Authorities tell News 9 the message was found in a set of iPads located in a specific classroom at the school. The content of the message still has not been disclosed.

The OKC Public Schools Information Technology (IT) department is working to determine the source of the threat. OKC Police were also called to the scene.

The case remains under investigation.