11.   Accident investigators are still not sure what caused the break-up of the plane.

12.   Nevertheless, there may be special reasons why clustering may be a useful technique, such as when an investigator is interested in certain subgroups of the population.

13.   If the investigators are satisfied that their suspicions are correct, arrests and charges will follow.

14.   Investigators are still at the scene in Woodside Road, trying to establish the cause of the blaze.

15.   Accident investigators have been at the scene this morning trying to piece together what happened.

16.   Human rights investigators were interviewing two witnesses to the killings, he said.

17.   American and Mexican investigators were unable to identify where Barron was born.

18.   Although investigators are interested in the latest theory, they emphasized that they are far from declaring a definitive cause.

19.   American investigators have been skeptical of that view and have at times expressed frustration over their inability to directly interview witnesses or suspects in the case.