"...the Oct. 17 explosion at the Ludwigshafen plant in Germany was likely caused by a contractor error...workers were 'carrying out scheduled maintenance on an empty pipeline'...investigators on Thursday found a cut in a nearby pipeline containing flammable gas. As such, BASF says the deadly blast was likely caused when a contractor mistakenly cut the wrong pipeline."
All too common in large process plants where piperacks can have dozens of similar-sized pipes.
Over here the normal practice is for a competent person to pre-mark the cut location with two bands of tape, the cut being made between the two bands. That's not to say that the competent person can't get it wrong, but it reduces the chance of a welding crew mis-identifying the pipe to be worked on.