SIOUX FALLS, S.D. (AP) - Two inmates accused in an attack that left a South Dakota prison guard hospitalized have pleaded not guilty.

Twenty-eight-year-old Carlos Green and 24-year-old Garrett Dumarce made their initial court appearances Thursday in Sioux Falls.

Authorities say Cpl. Zane Mathis was hospitalized April 20 with a broken jaw and facial cuts after he was punched several times in the head.

Green is charged with aggravated assault of a corrections employee. He faces life in prison.

Dumarce is charged with aiding, abetting or advising aggravated assault against a corrections employee. He could face up to 50 years in prison.

Copyright 2013 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

More From KXRB