DES MOINES (AP) — Polk County prosecutors have added three new involuntary manslaughter charges, but dropped one of eight counts filed last month against a Des Moines doctor suspected of prescribing large amounts of narcotic painkillers to people who fatally overdosed.

Prosecutors filed the additional charges on Monday against Dr. Daniel Baldi. Defense attorney Guy Cook entered a not guilty plea on Cook’s behalf on Monday.

Court papers identify three people who died in May and in July and September of 2011. Prosecutors dropped a charge in a 2009 death because the statute of limitations said the case was too old to be prosecuted.