Police and state prosecutors searched Sauerland's office, as well as those his personal aide and two other colleagues.
The city of Duisburg spoke of a handover “that had been previously arranged with the public prosecutor's office.”
“It was not a raid,” said Duisburg head prosecutor Rolf Haferkamp.
Soon after the deadly event on July 24, investigators received 37 file folders on the Love Parade from the city. Prosecutors realised that some information necessary for their investigation was missing, and therefore asked the city to hand over additional documents.
Thirteen women and eight men died in a stampede at the Love Parade techno festival after crowds built up in a tunnel leading to the dance area.
Blame has been laid on organisers, whose security arrangements for the event were lacking. Sauerland has also been the target of much public ire. He has come under intense pressure to resign but has refused to do so, even though he did admit to knowing about security concerns before the event.