Police in western Germany raided several offices and houses as part of an investigation into the deadly floods last summer.
The searches focused on the owner of an open pit mine in Erftstadt, near the city of Cologne, according to the DPA news agency.
Five people from the mine’s operating company are also being investigated, as well as four workers from the regional district council.
Prosecutors are investigating whether the suspects negligently caused a flood at the mine and endangered the facilities.
According to the investigation, a gravel quarry at the mine was filled with water last July due to insufficient flood barriers.
Later, the water caused the soil around the well to collapse during heavy rains, which had flooded the nearby Erft River.
Subsequent floods damaged several buildings in the town, but have not been directly linked to any victims.
More than 20 houses and offices were searched by 140 policemen on Tuesday, led by the prosecutor’s office in Cologne. The ten suspects are between 29 and 65 years old, but their names have not been released.
More than 180 people died and hundreds more were injured during last year’s devastating floods in Germany and Belgium.