NEW : 20 people are dead and 100 are injured . Indonesia 's railway ministry says one train hit another from behind . Survivors say the first train was stationary when it was struck . The cause of the accident is unclear .
NEW : 36 people are dead and 26 are injured . Indonesia 's transport ministry says one train struck another from behind . Survivors say the first train was stationary when it was struck . The cause of the crash is unclear .