New Delhi (AFP) - Twelve people have been killed after two packed trains derailed while crossing a bridge hit by floods in central India overnight Wednesday, authorities said, highlighting again safety problems with the nation's crumbling railway network.Rescuers have been searching in darkness for passengers feared trapped on the trains that were travelling in opposite directions when some of their carriages derailed in Madhya Pradesh state, the officials said. West Central Railway spokesman Piyush Mathur said several hundred people have been rescued after the trains derailed within minutes of each other near the town of Harda at about 11.30 pm on Tuesday. "There are 12 casualties," Mathur told the CNN-IBN network, adding that the death toll could rise.Another 25 people have been injured, a second official said, adding that the carriages have not fallen into the river.One of the trains travelling from the financial city of Mumbai appeared to have been hit by a sudden surge of water on the swollen Machak river, derailing the last four to five carriages, railway ministry spokesman Anil Saxena said. The other passenger train, travelling to Mumbai from the eastern city of Patna, was also hit by water, with the engine and the first two to three carriages derailing, he said. "There is some suggestion of flash floods on the tracks that caved the tracks.