An 85-year-old woman has been found dead in her home in northeastern Japan and police are investigating the incident as a possible robbery and murder, officials said Saturday.

Yasuko Komatsu's son found her collapsed in the hallway near the front door of her home in Iwaki, Fukushima Prefecture, when he visited Friday after being unable to contact her. Autopsy results showed her death was caused by head trauma resulting from her being struck with some kind of weapon, police said.

The entire house had also been ransacked, police said. Komatsu lived alone.

Police said there is no indication at this stage that this incident is related to a string of robberies that have taken place across Japan since last year, including a Jan. 19 case in the city of Komae in Tokyo that led to the death of a 90-year-old woman.