11.   The memo warned that poorly screened volunteers could cause a tragedy.

12.   There was speculation the tragedy was caused by a flat tire.

13.   Traditional Asian medicine can split families, produce miracles or cause tragedy, depending on your perspective.

14.   But it turned down a demand for an official apology, saying it remained unclear what caused the tragedy.

15.   Defense Minister Pavel Grachev, telling parliament the tragedy was caused by mistakes of the military leadership, said he was prepared to resign if asked.

16.   French police were questioning seven photographers, looking into whether any of them may have caused the tragedy.

17.   French police placed into formal custody seven photographers who had previously been detained, looking into whether any of them may have caused the tragedy.

18.   Grachev, telling parliament the tragedy was caused by mistakes of the military leadership, said he was prepared to resign if asked.

19.   Human rights groups blame both the rebels and the Angolan army for causing the tragedy by burning villages and forcing residents to flee.

20.   Human rights groups blame both the rebels and the Angolan army for having caused the tragedy by burning villages and forcing residents to flee.