Eastern Correctional Institution is on lockdown after officials said an inmate was found under the influence of an unknown substance Saturday afternoon and three staff members became ill after coming into contact with that inmate.
Officials with the North Carolina Department of Corrections said four people were sent to the hospital, and all were released by the following day.
Officials said the offender was transferred to Central Prison in Raleigh.
The prison in Greene County remains on lockdown because officials are still unsure what the substance is but the SBI is investigating.