Three adults and the child were killed on the A3 between Rüsselsheim and Cologne when their car was shoved under a truck by another vehicle as it approached a service station.
Rhineland police said they were still trying to figure out what caused the minibus to smash into the car, pushing it with ‘considerable force' under the trailer of the truck.
A spokesman said the car was so badly crushed in the accident that there was no way anyone inside could have survived. The identity of those involved has not yet been determined.
Three young men were killed in a separate incident on the A4 near Hermsdorf Ost in Thuringia. A police spokesman in Gera said one young man died at the scene while two others died shortly afterwards in hospital. They were in a car with two other young men who survived the crash but were seriously injured.
Their car came off the road, smashed into the ditch and was catapulted back onto the road, where it came to a halt. The three who died, aged 20, 21 and 23, were thrown out of the car during the crash while the 19-year-old driver and a 17-year-old remained in the car and survived.