The bodies belonged to five men and one woman, all in their 20s.

Authorities suspected the six met over the internet before dying together on Thursday night in a forested area about 50 miles north west of Tokyo.

In a similar case earlier this week, a man and two women in their 20s and 30s were found dead in Aomori, 360 miles north east of Tokyo. The three also died by inhaling charcoal fumes in a car.