While inspecting an Eternit roof, two craftsmen broke through the roof in Mannheim's Rheinauhafen and fell eight meters into the depth.
The roofers were critically injured between the ages of 31 and 43, the police said on Monday.
One of the two was flown to a clinic by a rescue helicopter.
Mannheim - The other man came to a hospital in an ambulance after being resuscitated.
The Mannheim trade supervisory office is involved.
dpa