(Reuters) - A family of six was found dead inside a Michigan home and officials said on Sunday they believed carbon monoxide was to blame.

Four children, aged between 2 and 11-years-old, were among the dead who were found in separate rooms of the Fenton Township house, Genesee County Sheriff Robert Pickell told reporters on Sunday.

“It’s very difficult,” Pickell said in a recording of the on-site news conference published online by local broadcaster WJRT. “No matter how many investigations you conduct, seeing young children and an entire family wiped out is a very, very sad thing.”

He said the family seemed to have a generator running in the house, some 50 miles (80 km) northwest of Detroit, after a power outage in the area on Friday. He said the husband’s father was the one who called police on Sunday.

He said an investigation was underway.