Berlin - Ultrasound checks have discovered a second axle in Germany's bullet-train fleet contains a tiny crack that some safety experts fear could have widened into a break and caused a rail disaster.

The Deutsche Bahn company, which has halted operations by dozens of ICE high-speed trains for checks, disclosed the discovery Friday after the company's chief executive, Hartmut Mehdorn, said an "anomaly" had been found.

The first such crack deeper than the safety limit of 2 millimetres was discovered in a drive axle in mid-October.

If one of the 32 drive axles on an ICE were to fail at more than 200 kilometres per hour, a train might derail.

The defects and the suspension of its normally smooth timetable have turned into a major embarrassment for Bahn, Germany's national rail company, which is already under fire over fare rises planned for December 14.

Both cracks were found in the axles of ICE-T trains, a variant on the series in which the trains tilt slightly on curves. Up to 40 trains of the overall electric-powered ICE fleet are idle because of the tests.

Bahn said it would be operating shorter or slower trains on key routes for the next two months. (dpa)