BERLIN (AP) — German federal prosecutors say they are taking charge of the investigation into the suspected sabotage of a railway communication system that brought trains to a standstill Saturday across northwestern Germany.

The federal prosecutors office said Thursday it is taking over the probe from state investigators due to the gravity of the case.

Officials said Monday that cables were severed deliberately in a Berlin suburb and 440 kilometers (275 miles) away in the western Germany town of Herne.

Trains in the northwestern states of Hamburg, Schleswig-Holstein, Lower Saxony and Bremen were halted for nearly three hours on Saturday morning. Railway operator Deutsche Bahn said that was necessary because a digital train radio system failed.