A Natrona County man is accused of sexually abusing three girls over a 20-year period.

Forty-three year old Michael Griswold has pleaded not guilty to six counts of first degree sexual abuse of a minor (maximum 50 years in prison on each count, if convicted), two counts of first degree sexual assault (maximum 50 years in prison on each count, if convicted), one count of third degree sexual assault (maximum 15 years in prison, if convicted), one count of attempted third degree sexual assault (maximum 15 years in prison if convicted), and one count of immodest or indecent liberties with a minor (maximum 10 years in prison if convicted).

Investigators with the Natrona County Sheriff's Office say they were contacted in August 2017 in which a woman approached with information she received about a possible sexual assault of a relative.

The relative was first allegedly assaulted when she was 11 or 12.

The woman asked the girl's sister if that happened to her.

The sister didn't believe it, but later said she had been molested as well.

Another girl was afraid of coming forward.

The abuse of that girl started when she was 7.

She is now an adult and has a professional presence in the area.

The various crimes are alleged to have occurred between January 1992 and October 2012.

Griswold is awaiting trial on $250,000 bond.