VENANGO TWP — A trooper turned up more than three dozen marijuana plants growing inside a house on Pisor Road while investigating an accidental drug overdose death, authorities said.

State police Friday charged Frank Thomas Mercurio, 59, with tending to the illegal crop at his house. Mercurio faces felony and misdemeanor counts of drug possession.

Police four months ago by chance happened upon the plants after going to the defendant's home as part of the investigation into his son's death.

Scott Mercurio, 31, died April 3 at the house. Investigators later determined the younger Mercurio died from an accidental Fentanyl overdose, a spokeswoman for the Butler County coroner's office said.

Fentanyl is an opiate-based painkiller that is considered more potent than heroin.

While at the house investigating the death, troopers found 38 marijuana plants in a room, a lighting system, electric temperature and humidity gauge, and packages of unplanted seeds, according to court documents.

The defendant when first confronted about the contraband, denied any knowledge of the plants. But investigators doubted that denial because of the scope of the grow operation and the size of the house.

A police affidavit noted, for example, that to get to the bathrooms in the house, the occupants "had to walk by this grow operation."

The evidence was seized and sent to the state police crime lab for analysis. Tests confirmed the plants were marijuana.