Cologne's chief of police, speaking to reporters at a press conference on Wednesday, gave more information on the investigation into an explosive device found at the central train station in Bonn earlier in the week. The local police had expanded their search after spotting a potential suspect on video footage from a nearby eatery.

A light-skinned man was shown carrying a bag similar to the one found with an explosive device, Cologne Chief of Police Wolfgang Albers said.

The video footage used in the investigation came from the McDonald's in the railway station, not from the security cameras aimed at the platform, which were all out of order that day, according to the local Bonn newspaper "General-Anzeiger."

The police department of the city Cologne, which lies about 30 kilometers (18 miles) north of Bonn, has been heading the investigation in cooperation with German Federal Police and other security agencies.

Police Chief Albers also revealed new information regarding the analysis of the device found on site.

An explosion could have unleashed "a very dangerous fireball," he said.

It remained unclear whether the bomb plot had links to terrorism.

Prior to the announcement Wednesday, authorities had released a computer-generated composite picture of a suspect based on the description by a 14-year-old eyewitness. The picture shows a tall, thin, dark-skinned man between the ages of 30 and 35.

The bomb, which was found on Monday afternoon, brought railway travel to a standstill in the Bonn region as police cleared travellers from the area. Major delays disrupted both regional and long-distance trains during the evening rush hour.

kms/hc (dpa, dapd, AFP)