Fortescue derailment discussion

Sounds like Fortescue had a four day rail line outage - back online tomorrow:

"Multiple ore cars were derailed from a Fortescue Metals Group train track on Saturday, which are still blocking output to the miner’s only Pilbara port."

"...Fortescue said the derailment involved multiple wagons but declined to say how many or reveal additional details on the extent of the damage.It is understood the derailment happened about 150 kilometres south of Port Hedland, but Fortescue would not comment on the location."

"...an internal investigation was under way to determine the cause of the derailment.“No one was injured in the incident and there is no impact to members of the community,” she said."

"Fortescue expects to reopen the rail line on Wednesday. It said the derailment and four-day supply chain outage would not affect its iron ore shipments for December or the half-year to December 31.The company declined to comment on whether January shipments would be affected."

So offline at some point on December 30, offline Dec 31, Jan 1, and Jan 2.

Fortescue exported 192 million tonnes of iron ore last financial year. Let's say half a million tonnes a day, though some portion comes from the Iron Bridge 135km slurry pipeline.

Obvious qs: How do you recover from the missing supply? Does the company build a stockpile at port for this kind of thing? And, what caused the derailment?