A suspicious fire broke out late on Friday at railway tracks in the western city of Wuppertal, according to German rail operator Deutsche Bahn.

Cables were apparently cut and set alight deliberately, with state security investigators called to the scene to investigate after previous deliberate attacks in the same region.

What happened in Wuppertal?

A Deutsche Bahn (DB) spokeswoman told the dpa news agency that the fire appeared to have been fueled by an accelerant. Initial findings indicated cable sheathing had been set on fire near railway switches, the mechanisms that let a train move from one track to another.

Police described it as a "switch fire" large enough to have been noticed by a nearby resident, who informed authorities shortly before midnight.

Firefighters were able to extinguish the fire quickly, the website of local broadcaster Radio Wuppertal said.

While the flames affected three switches, the DB spokeswoman said the fire had not touched the switches directly. The spokeswoman confirmed two cables were severed "presumably deliberately” before being set on fire.

InfraGO, a DB subsidiary, reported on its website that cables were "damaged and ignited by third parties."

Despite the damage, DB said train traffic was barely disrupted.

How did authorities respond to the fire?

Federal police deployed state security investigators, who routinely step in when sabotage is suspected, once ordinary technical causes were ruled out. A police helicopter searched the area overnight for possible suspects, but authorities did not report any immediate arrests.

Investigators were collecting evidence from the site for forensic analysis.

Police have not publicly commented on possible motives. The incident is being treated as suspected arson against critical infrastructure.

The fire is the latest in a series of incidents targeting railway equipment in the western state of North Rhine-Westphalia.

Less than a month ago, incendiary devices were planted on a line between the cities of Düsseldorf and Duisburg. Those attacks destroyed cables controlling switches and signals and caused significant disruption to both regional and long-distance services.

Investigators are under pressure to determine whether the cases are linked amid concerns about security of transport infrastructure across the country.

Edited by: Louis Oelofse