SPRINGFIELD, Ill. (AP) — The FBI is investigating the death of an Illinois prison inmate.

In a statement, Illinois Department of Corrections spokeswoman Lindsey Hess says the incident occurred on May 17 at the Western Illinois Correctional Center in Mount Sterling. Hess says the inmate was airlifted to a regional hospital, placed in intensive care and later died. But she declined to provide any details about the incident, the inmate's name, when he died or the cause of death.

The statement says that "several" staff members have been placed on administrative leave and that "any activity that compromises" the safety of both staff and offenders will not be tolerated.

The FBI has only said that the investigation is ongoing.