Criminals have sabotaged railway signal boxes several times in recent months - sometimes with massive consequences for train traffic.
In four cases, the police have now identified suspects and searched apartments.
Leverkusen - After a series of signal box manipulations at the end of January, the police searched the homes of three suspects on Thursday morning.
The investigators of the State Security Criminal Inspectorate had accessed Bochum, Mönchengladbach and Viersen, the Cologne police and the Mönchengladbach public prosecutor said.
The three suspects, aged 22, 18 and 16, lived there.
The apartment of a 15-year-old in Herten, who is listed as a witness, was also searched.
The three men are suspected of having penetrated the technical rooms of signal boxes in Essen-Kray, Essen-Stadtwaldwende, Leverkusen-Küppersteg and Schwelm near Wuppertal on January 29.
The investigators said they willfully operated signal switches and thus ensured that the trains on parts of the rail network no longer had power.
Several trains would have had to stop because of this.
There were significant disruptions in rail traffic.
During the searches, the investigators said they seized data carriers such as computers and mobile phones, among other things.
A police spokeswoman said there were no arrest warrants for the suspects.
However, the men were taken to the station for further questioning.
According to their own statements, the investigators tracked down the three men who were friends by evaluating surveillance cameras, among other things.
What motives they could have had is still unclear.
The public prosecutor's office is investigating on suspicion of dangerous intervention in rail traffic.
Specifically, the investigators only accuse the three men of manipulating the signal box on January 29th.
However, the railway had been the target of saboteurs several times in the previous months.
On October 8th, unknown persons in Herne and Berlin cut the fiber optic cable of the internal railway mobile network, which is used, among other things, by the engine driver and control centers to communicate with each other.
As a result, rail traffic in northern Germany came to a complete standstill for several hours.
In December, the railway was again attacked by saboteurs: unknown persons broke into a switch house in the Dellwig district of Essen and severed cables in switch boxes.