Authorities said Wednesday they have not ruled out sabotage in the derailment of a speeding express train in central Madhya Pradesh that killed at least 67 passengers and injured 137 others.

Special relief trains rolled into the capital early Wednesday bearing survivors of the Tuesday crash along a remote stretch of track near Lalitpur, 280 miles south of New Delhi.Officials and witnesses said 12 passenger carriages of the 21-car train traveling north to New Delhi from southern Karnataka state inexplicably derailed as the locomotive sped through farmlands in the mostly rural state.