ARLINGTON, WA (MyBellinghamNow.com) – The FBI is investigating a series of threats made at a regional hospital.

Skagit Regional Health says that four separate threats were called into Cascade Valley Hospital in Arlington over the past few days.

The first threat was called in on the evening of Wednesday, April 23 with the most recent incident happening on the morning of Tuesday, April 29.

All four calls prompted lockdowns at the hospital.

The City of Arlington adds that they believe the threats are all connected to either a single person or group, and that other hospitals across the country are likely being targeted by them as well.

Extra security is being provided at Cascade Valley Hospital as the investigation continues.