OSAKA (Kyodo) West Japan Railway Co. was hit by another embarrassing revelation Wednesday that may call into question the railway's safety mindset.

Drivers of trains on central Osaka's belt line have been found to have taped over the in-cab speaker for sound alerts in apparent attempts to mute the sound, JR West sources said.

The sound alert — a voice recording saying, "Halt, halt" — comes from a speaker near the driver's seat. The automatic train stop system installed in trains issues the alarm every time a train approaches a station. If a driver fails to activate the brakes, the ATS stops the train.