SOMESET, Pa. (AP) — Authorities say an inmate at a western Pennsylvania prison assaulted two guards, seriously injuring one and prompting a lockdown at the facility.

Public information officer Christie Schenck says the 22-year-old inmate attacked a corrections officer assigned to a housing unit at State Correctional Institution-Somerset at about 7 p.m. Thursday. She says another corrections officer who came to the aid of the first officer was also assaulted.

Schenck says both officers were taken to Conemaugh Memorial Medical Center in Johnstown, where one remained hospitalized with serious injuries. She said she didn't believe a weapon was involved in the assault.

The prison was placed on lockdown indefinitely, with all visits canceled for Friday and Saturday.