1.   Investigators are still trying to determine the cause of the fire.

2.   Investigators are trying to pinpoint the cause of the fire.

3.   Last night, accident investigators were still trying to find out what exactly caused the disaster.

4.   The man died instantly and his name was withheld while investigators tried to locate relatives.

5.   Investigators are trying to find out what caused the rocket to blow up in midair.

6.   Accident investigators are still trying to piece together the events that led up to the crash.

7.   Investigators are trying to establish if anyone knew about these problems before the accident.

8.   To this day, investigators are still trying to piece together the evidence which will reveal precisely what went wrong.