The company says systems may have become overloaded after a high-voltage transmission line was shut down over a river to let a ship pass.
Resulting power outages affected as many as ten million people in Germany, France, Italy, Austria, Belgium and Spain.
The outages raised fresh questions about the reliability of Europe's interconnected power grids.
Italy's prime minister says the incident shows that Europe may need to strengthen its coordination of power supplies.
But a utilities official insisted that Europe's power network had worked well.
He said that's how the region was able to avoid a "total blackout."
Associated Press