A high-speed German train hit six metal slabs bolted to rails by unknown assailants but avoided derailment near the western town of Dortmund, police said on Sunday.
The driver of the Intercity Express (ICE) train carrying 200 passengers was able to slow the train sharply before hitting the slabs weighing 17.5 kilos (38.5 lb) each, police said.
"At this point we don't believe that this was a terrorist attack," said state prosecutor Henner Kruse at a news conference in Dortmund.
State prosecutors said they had no clues on suspects or the motives behind the Saturday morning incident near the Kamen motorway junction. No one was hurt.
The train driver spotted the slabs covered by a blue trash back and hit the emergency brakes, slowing the train to about 90 kph (55 mph). Trains usually reach 160 kph on the track there.