1.   A bulldozer digging a trench for a water line punctured the pipeline.

2.   Workers building a new subway line had accidentally punctured a pipeline carrying liquefied petroleum gas.

3.   The thieves, usually carrying buckets, puncture the pipeline using sharp metal objects.

4.   While exactly what set off the blast remains unclear, state oil officials blamed a fuel-smuggling ring for puncturing the pipeline to siphon off gasoline.

5.   What sparked the explosion remained unclear although witnesses said the pipeline had been punctured by vandals days earlier.

6.   Witnesses said the pipeline had been punctured days earlier.