11.   Officials blamed signal failure for most of the accidents.

12.   Officials have blamed signal failures for most of the accidents.

13.   Officials now say a signal failure may have put both trains on the same track, PTI reported.

14.   Officials said they believed a signal failure may have caused both trains to be on the same track, the BBC reported.

15.   Officials blamed signal failures for most of the accidents.

16.   Signal failure may have put both trains on the same track, officials told the BBC.

17.   The two crowded trains, mainly carrying peasant farmers between market towns and their homes, apparently collided on the single track line after a signal failure.

18.   A Tamil Nadu government spokesman said that signal failure was believed to be the cause of the accident.

19.   A Tamil Nadu government spokesman said signal failure was believed to be the cause of the accident.

20.   Officials mostly blame signal failures.