Argentina's energy secretary says improper reprogramming of the electricity system following installation of a bypass on a major transmission line caused the power outage that left tens of millions of people in three nations without power.
Gustavo Lopetegui told a congressional committee Wednesday that the Transener company that operates the lines failed to account for and reprogram an emergency system after replacing a high-voltage tower. So when a short circuit hit the grid, the suddenly imbalanced system didn't adjust to it as planned and the grid collapsed.
Transener issued a statement of apology later Wednesday.
Many people in Argentina, Uruguay and Paraguay were left without power for 14 hours on June 16.
Lopetegui says regulators will determine what penalties to apply.