IRON RIVER — Michigan State Police say a February house explosion in Iron River that left an 80-year-old man dead was the result of “human intervention with unknown intent.”

The blast at 820 Cayuga St. was reported at about 9:30 p.m. on Feb. 10. The house was completely demolished and debris was scattered as far as three blocks away. Killed was Gregory Dierkes, 80, who had just moved into the home after moving to Iron River from Florida.

In the MSP investigation report, a specific source of the explosion was not given but it was noted that the furnace, water heater and stove all ran on natural gas. According to DTE, gas flow increased significantly in the four hours leading up to the explosion.

There was reportedly a bright flash in the kitchen before the home exploded.

The medical examiner’s report said that Dierkes died from a tertiary blast injury.

Troopers from the Iron Mountain post and neighboring posts responded to the blast along with the Iron County Sheriff’s Department, Iron River Fire Department and several other fire departments from Iron and Dickinson counties. MSP K-9 units and the MSP district fire investigator also assisted. Iron River City Police led the investigation with assistance from the MSP.

More than 100 windows were broken in neighboring residences as debris was scattered across at least a three-block radius.