Assumed to be ferromagnetic, and considered unsafe if located within 5mm of a solid organ or of a 3rd order or more proximal arterial/venous branch of the aorta/IVC.
Take precautions to limit and monitor for symptoms of thermal injury.
Embedded metallic foreign bodies, especially if in place for a long period of time, may be anchored in place by scar tissue. Use clinical judgment in assessing the potential risks and benefits of undergoing MRI.
Bottom line: Requires radiologist determination on case by case basis