Detectives found the flag in support of the brutal terror gang and a text in Arabic near the site of a Berlin railway track that had been tampered with. Investigators are probing if the flag belongs to those responsible for damaging the railway’s overheard contact wires. Following the incident, authorities found a torn steel cable and damaged wire at the train track on Sunday.
A police spokesman said: “Since the beginning of the investigation, several pieces of evidence have been secure.”
Officers are investigating if there is any connection between the Berlin incident and a similar case two months ago.
In October, police found steel wire pulled across train tracks in Bavaria with fears of an ISIS terror cell was plotting to derail a high-seed train.
According to Bild, German authorities found a threatening letter written in Arabic promising more attack.
In this week’s incident, train operator Deutsche Bahn informed the police and local train services were temporarily interrupted.
Europe remains braced for terror threats after this month’s Strasbourg attack by an Islamist extremist killed five people and wounded 11.
ISIS-supporting maniac Cherif Chekatt, 29, was shot dead by French police after opening fire on people near the city’s Christmas market.
Chekatt, who was on a French list of possible extremist security risks, armed himself with with a handgun and a knife as he launched his murderous assault.
He fled in a taxi while wounded and later opened fire on officers before being shot dead.
Nine days after his death, a video was found showing Chekatt pledging allegiance to Islamic State.
In recent years, Germany has suffered a number of attacks by Islamist terrorists.
The worst attack in December 2016, saw 12 people murdered and 48 injured when a terrorist driving a truck ploughed into Berlin’s Christmas market.