Submission + - Samsung spilled up to 763K gallons of sulfuric acid waste into Austin tributary (kxan.com) 1
They have not stated the cause of the spill.
From the article:
Spill investigators and scientists took a look at the area Jan. 18-19 and saw iron staining in the tributary channel consistent with a low pH environment, the memo states. WPD says it was in this tributary stretch from the Samsung plant to the main branch of Harris Branch Creek that WPD staff found no surviving aquatic life, including fish.