A weekend train derailment keeps work crews busy cleaning up in the Altoona railyard. A Union Pacific spokesperson says about a dozen cars derailed Saturday afternoon. Altoona Fire Chief Mark Renderman says no hazardous materials were found in the empty rail cars. No injuries were reported. W-E-A-U / T-V reports roads near the derailment stayed open as the cleanup work was conducted. Investigators are trying to determine the cause of the accident.