Crews work at the scene of a train derailment near Littlerock, southeast of Palmdale in the Antelope Valley. The train derailed Wednesday afternoon while traveling from Roseville to Colton. (Irfan Khan / Los Angeles Times)
A repair team works on the tracks at the scene of a train derailment near Littlerock, southeast of Palmdale. Twenty-one cars of the 68-car train derailed on Wednesday. (Irfan Khan / Los Angeles Times)
Among the train cars that derailed Wednesday were six that typically carry hazardous materials, but Union Pacific said they were all empty. (Irfan Khan / Los Angeles Times)
Repair teams work on the tracks. (Irfan Khan / Los Angeles Times)
A nearby resident views the site of a train derailment near Littlerock, southeast of Palmdale. Concern over a possible hazardous chemical spill led authorities to evacuate more than 250 homes Wednesday afternoon; the evacuees were told around 2 a.m. Thursday that they could go home. (Irfan Khan / Los Angeles Times)
