MINNEAPOLIS (AP) - The former mayor of Stillwater has pleaded guilty to tax fraud conspiracy.

Ken Harycki entered the plea in federal court Thursday in Minneapolis. Prosecutors say Harycki knowingly prepared false tax forms to help the owners of health care companies conceal between $1 million and $2.5 million in tax liabilities.

The Internal Revenue began investigating Harycki in October 2012. A federal search warrant affidavit says Harycki created shell companies for the owners and filed false tax returns on their behalf.

Sentencing guidelines call for 36 to 42 months in prison. A sentencing date has not yet been set.