The crash, on the B469 near Niedernberg in northern Bavaria, happened shortly before midnight when two cars, a Fiat and a Mercedes, collided. The Fiat Punto was carrying four members of the same family, three of whom died.
The 26-year-old driver of the Mercedes, who was from Aschaffenburg, suffered minor injuries.
Police said on Friday morning that the cause of the crash was not yet known. But they added in a statement: ”There is evidence suggesting the Mercedes which was driving in the same direction as the Fiat Punto hit it from behind at high speed.”
Officers said it appeared the Mercedes had just overtaken another vehicle when it hit the Punto carrying the family.
“The force of the impact was so strong that the small car [the Punto] was thrown off the road and came to a stop in a field after 100 metres, completely damaged,” police said.
The 51-year-old driver, his 49-year-old wife and their 15-year-old son died. Their 20-year-old son was taken to hospital with serious injuries.
Police said around 60 emergency service personnel were called to the scene and the road was closed for almost four hours.