Four people were seriously hurt. Ten others had minor injuries. The two ACE personnel on the train were not among those injured. The passengers were checked by after evacuation and the uninjured riders were transported to the Alameda County Fair in Pleasanton. Francisco Castillo Jr., a Union Pacific spokesman, said in an interview with local news outlets Tuesday morning that the company sent investigators to the scene Monday night. The derailment followed a three-day storm. Preliminary investigation shows that a mudslide triggered by days of rain likely caused a Bay Area commuter train to derail. It was estimated that it could take “several days” to clear the scene and have service restored.