Fabrication plants jointly run by Kioxia and Western Digital accidentally used a contaminated chemical to manufacture 3D NAND non-volatile flash memory.

The issue impacted at least 6.5 exabytes of NAND supply, and potentially as much as 16 exabytes - a significant proportion of global supplies.

The two companies operate six fabs in Japan in Yokkaichi, Mie prefecture, and Kitakami, Iwate prefecture. All of the fabs used the unidentified chemical from an unknown supplier, contaminating production. Measures are underway to restore production.

"Western Digital's current assessment of the impact is a reduction of its flash availability of at least 6.5 exabytes," the company said in a statement. That would represent more than a quarter of the NAND it sold in the fourth quarter.

We don't know how long remediation efforts will take, and whether production lines need to be shut down so that systems and pipes can be cleaned. This could further impact supply. The two companies are responsible for around a third of global NAND flash supplies.

Recently, Western Digital has informed customers that all shipments of their flash products will be subjected to a 5% surcharge.