Kent County Undersheriff Jon Hess said Willie Lee Williams, 20, attacked the female jail officer early Friday. He said Williams didn't have a weapon, but he described the incident as a serious assault.
The officer was treated and released from a hospital. Hess declined to release her name or any details about her injuries.
Hess said Williams was hiding in a room typically used by inmates during the day. The undersheriff said other inmates were able to help the officer because Williams struck an electrical panel that opened cells.
Williams is in jail facing robbery charges. He'll now face additional charges in the assault.