Eight people, including six children, were found dead in a Michigan home after a fire, some with gunshot wounds, authorities said Friday.

Police and firefighters responded shortly before noon to a house fire in Grand Haven Township, on the eastern shore of Lake Michigan. When they entered, they found the bodies, Capt. Jacob Sparks of the Ottawa County Sheriff’s Office said at an afternoon news conference.

Sparks said authorities have not yet fully identified all of the victims and do not have an official cause of death. The children’s ages ranged from 5 to 15 years old, he said.

He did not say how many people had gunshot wounds.

“It’s a complicated scene, a complex scene,” Sparks said.

He said investigators were not looking for outside suspects and that one theory so far is a murder-suicide. He said everyone who lived in the house appeared to have died.

Sparks said the fire was “suspicious” and there was reason to believe it was intentionally set. Michigan State Police arson investigators are assisting at the scene, he said.

Grand Haven Township has a population of approximately 18,000 and is 25 miles (40 kilometers) west of Grand Rapids.