Lathen, Germany ? Investigators sought Saturday to determine why safety rules didn’t prevent a high-speed magnetic train from powering up and speeding into a maintenance vehicle still on the elevated test track, killing 23 people.

Alexander Retemeyer, a prosecutor speaking for investigators, said they were focusing on what happened in the 20-mile track’s control center, where the required two employees were on duty.

Friday’s crash near Lathen in northwestern Germany was the first involving a train using magnetic levitation, or maglev, in which the train rides on a magnetic field without touching rails. The lack of friction allows speeds as high as 270 miles per hour.

The controllers were supposed to go through several layers of checks to make sure the maintenance vehicle was off the track after its daily inspection, Retemeyer said. Only then were they to turn on the electricity enabling the train driver to start, he said.

Investigators examined the control room log book and discovered the maintenance truck was where it was supposed to be.