Three Ohio residents have pleaded not guilty to felony assault charges stemming from an explosion that critically injured a New York state prison guard outside his home.

Authorities say the suspects were taken to Oneida County for an appearance Monday in the town court in Floyd. Correction officer Alan Dobransky suffered serious injuries May 29 when a cardboard box exploded outside his home.

Police say 58-year-olds Keith Seppi and Cindy Shields and 63-year-old Donna Seppi were arrested June 7 at their homes in Conneaut, Ohio.

Authorities say the explosive was intended to stop the 53-year-old Dobransky from reporting an elder care scam against his mother in Ohio.

The suspects are being held at the county jail on $250,000 bail. They're due back in court June 20 for a felony hearing.