Strong winds blew sand and earth onto the four-lane A19 autobahn near Rostock in Mecklenburg-Western Pomerania state, severely hindering visibility for motorists and causing accidents in both directions.
Northbound, three lorries and 17 cars slammed into each other and were engulfed in flames, possibly caused by chemicals on one of the trucks catching fire, police said.
A spokesman said the toll could still rise, as rescue workers were still searching for bodies in the smoking, mangled wreckage.
On the other side of the road at least 30 cars crashed, but there were no fatalities. Strong winds impeded rescue workers and the road was closed in both directions until further notice.
More than 80 people were injured, some of them seriously.
The Bild daily on its website put the death toll at at least 10.