ALISO VIEJO ( — St. Mary of All Angels, a school in Aliso Viejo, was on the receiving end of an emailed-in threat Monday.

Authorities were immediately contacted by school officials and arrived on campus to begin conducting a thorough investigation.

READ MORE: Woman, 4 Children Shot And Killed In Lancaster Home

The school reportedly held all activities inside as the investigation proceeded Monday.

READ MORE: Man Killed After Large Tree Topples Onto Encino Home

Sheriff’s deputies assessed that the campus was secure, and school security personnel were in cooperation with authorities.

It was not immediately clear whether the threat was valid or whether the school will cancel classes throughout the week.

MORE NEWS: A Dozen People Displaced After Fire Burns South LA Apartment Building

The details of the threat were not immediately released.