This mishap happened in connection with a lifting operation being performed by the pipehandling crane on the installation.
A length of seven-inch production tubing, weighing 572 kilograms, fell 13.5 metres and landed in a stairwell.
No people are reported to have been injured during the incident.
Clarifying the course of events and identifying the direct and underlying causes are among the aims of the PSA’s investigation.
The investigation will result in a report which will be published on the ptil.no website.