Dusseldorf - The German railway company Deutsche Bahn was conducting urgent tests Friday on the axles of all its ICE 3 bullet trains, two days after one snapped as a train left a station.

Bahn said it cancelled 60 trips on its national express network on Friday. Slow trains took over many routes. More cancellations would be necessary over the weekend.

The mark-3 version of Germany's inter-city express (ICE) electric trains cruises at more than 200 kilometres per hour and can accelerate to 300 on suitable sections of specially reinforced track. It also operates between Frankfurt and the French capital Paris.

A broken wheel derailed an earlier ICE version on June 3, 1998, killing 101 people in one of Germany's worst rail disasters.

The axle defect was discovered Wednesday after a passenger on an ICE from Frankfurt to Cologne complained to a conductor of strange noises, and said he was told, "Don't worry. That doesn't mean anything."

Deutsche Bahn said Friday a conductor activated the emergency brake as the train left Cologne. At slow speed, part of the train derailed. Nobody was hurt. Bahn said it was not clear if the axle break happened before or after the derailment.

After passengers laid a complaint with police, public prosecutors launched an inquiry Friday to see if anyone had committed the crime of endangering public transport.

Bahn's chief passenger services officer, Karl-Friedrich Rausch, said the passenger's concern had been acted on, since it prompted the conductor to halt the train. He described the accident as "highly unusual." (dpa)