1.   An explosion could blow out a flare and rupture pipelines, injecting quantities of the raw toxin into the environment.

2.   The spectacular fire ruptured the pipeline, destroyed six homes and injured four firefighters.

3.   They could rupture a pipeline.

4.   Authorities are unsure how the pipeline was ruptured.

5.   Two buses collided head-on Wednesday and one ruptured a pipeline, setting off an explosion and fire that killed dozens of people, officials said.

6.   Flood-weary Texas residents had to cope with fire and smoke Thursday as floodwaters apparently ruptured a pipeline along the San Jacinto River, witnesses and officials said.